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THE FAUNA OF BRITISH INDIA,

INCLUDING

CEYLON AND BURMA.

Published under the authority
of the Secretary of
State for India in Council.

EDITED BY A. E. SHIPLEY, M.A.,
Sc.D., HON. D.Sc., F.R.S.

FRESHWATER SPONGES,

HYDROIDS & POLYZOA.

BY

N. ANNANDALE, D.Sc.,

superintendent and trustee (ex
officio) of the indian museum,
fellow of the asiatic society
of bengal and of the calcutta university.

LONDON:

TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET.

August, 1911.

PRINTED AT TODAY & TOMORROW'S PRINTERS &
PUBLISHERS, FARIDABAD

CONTENTS.

EDITOR'S PREFACE.

Dr. N. Annandale's volume on the Freshwater Sponges, Polyzoa, and
Hydrida contains an account of three of the
chief groups of freshwater organisms. Although he deals mainly with
Indian forms the book contains an unusually full account of the
life-history and bionomics of freshwater Sponges, Polyzoa, and
Hydrozoa.

I have to thank Dr. Annandale for the great care he has
taken in the preparation of his manuscript for the press, and also the
Trustees of the Indian Museum, Calcutta, for their kindness in placing
material at the disposal of the Author.

A. E. SHIPLEY.

Christ's College, Cambridge,

March 1911.

SYSTEMATIC INDEX.

GENERAL INTRODUCTION
TO THE VOLUME.

Although some zoologists have recently revived the old
belief that the sponges and the cœlenterates are closely allied,
no one in recent times has suggested that there is any morphological
relationship between either of these groups and the polyzoa. Personally
I do not think that any one of the three groups is allied to any other
so far as anatomy is concerned; but for biological reasons it is
convenient to describe the freshwater representatives of the three
groups in one volume of the "Fauna."

Indeed, I originally proposed to the Editor that this volume should
include an account not only of the freshwater species, but of all those
that have been found in stagnant water of any kind. It is often
difficult to draw a line between the fauna of brackish ponds and marshes
and that of pure fresh water or that of the sea, and this is
particularly the case as regards the estuarine tracts of India and
Burma.

Pelseneer^[A] has expressed the
opinion that the Black Sea and the South-east of Asia are the two
districts in the world most favourable for the study of the origin of a
freshwater fauna from a marine one. The transition in particular from
the Bay of Bengal, which is much less salt than most seas, to the
lower[Pg
2]reaches of the Ganges or the Brahmaputra is peculiarly
easy, and we find many molluscs and other animals of marine origin in
the waters of these rivers far above tidal influence. Conditions are
unfavourable in the rivers themselves for the development and
multiplication of organisms of many groups, chiefly because of the
enormous amount of silt held in suspension in the water and constantly
being deposited on the bottom, and a much richer fauna exists in ponds
and lakes in the neighbourhood of the rivers and estuaries than in
running water. I have only found three species of polyzoa and three of
sponges in running water in India, and of these six species, five have
also been found in ponds or lakes. I have, on the other hand, found
three cœlenterates in an estuary, and all three species are
essentially marine forms, but two have established themselves in ponds
of brackish water, one (the sea-anemone Sagartia schilleriana)
undergoing in so doing modifications of a very peculiar and interesting
nature. It is not uncommon for animals that have established themselves
in pools of brackish water to be found occasionally in ponds of fresh
water; but I have not been able to discover a single instance of an
estuarine species that is found in the latter and not in the former.

For these reasons I intended, as I have said, to include in this
volume descriptions of all the cœlenterates and polyzoa known to
occur in pools of brackish water in the estuary of the Ganges and
elsewhere in India, but as my manuscript grew I began to realize that
this would be impossible without including also an amount of general
introductory matter not justified either by the scope of the volume or
by special knowledge on the part of its author. I have, however, given
in the introduction to each part a list of the species found in stagnant
brackish water with a few notes and references to descriptions.

Biological Peculiarities of the
Sponges, Cœlenterates, and Polyzoa of Fresh Water.

There is often an external resemblance between the representatives of
the sponges, cœlenterates, and polyzoa that causes them to be
classed together in popular phraseology as "zoophytes"; and this
resemblance is not merely a superficial one, for it is based on a
similarity in habits as well as of habitat, and is correlated with
biological phenomena that lie deeper than what are ordinarily called
habits. These phenomena are of peculiar interest with[Pg 3] regard to
difficult questions of nutrition and reproduction that perhaps can only
be solved by a close study of animals living together in identical
conditions and exhibiting, apparently in consequence of so living,
similar but by no means identical tendencies, either anatomical or
physiological, in certain directions.

One of the most important problems on which the study of the sponges,
cœlenterates, and polyzoa of stagnant water throws light is that
of the production of resting buds and similar reproductive bodies
adapted to withstand unfavourable conditions in a quiescent state and to
respond to the renewal of favourable conditions by a renewed growth and
activity.

Every autumn, in an English pond or lake, a crisis takes place in the
affairs of the less highly organized inhabitants, and preparations are
made to withstand the unfavourable conditions due directly or indirectly
to the low winter temperature of the water: the individual must perish
but the race may be preserved. At this season Hydra, which has
been reproducing its kind by means of buds throughout the summer,
develops eggs with a hard shell that will lie dormant in the mud until
next spring; the phylactolæmatous polyzoa produce statoblasts, the
ctenostomatous polyzoa resting-buds ("hibernacula"), and the sponges
gemmules. Statoblasts, hibernacula, and gemmules are alike produced
asexually, but they resemble the eggs of Hydra in being provided
with a hard, resistant shell, and in having the capacity to lie dormant
until favourable conditions return.

In an Indian pond or lake a similar crisis takes place in the case
of most species, but it does not take place at the same time of year in
the case of all species. Unfortunately the phenomena of periodic
physiological change have been little studied in the freshwater fauna of
most parts of the country, and as yet we know very little indeed of the
biology of the Himalayan lakes and tarns, the conditions in which
resemble those to be found in similar masses of water in Europe much
more closely than they do those that occur in ponds and lakes in a
tropical plain. In Bengal, however, I have been able to devote
considerable attention to the subject, and can state definitely that
some species flourish chiefly in winter and enter the quiescent stage at
the beginning of the hot weather (that is to say about March), while
others reach their maximum development during the "rains" (July to
September) and as a rule die down during winter, which is the driest as
well as the coolest time of year.

[Pg
4]The following is a list of the forms that in Bengal are
definitely known to produce hard-shelled eggs, gemmules, resting-buds,
or statoblasts only or most profusely at the approach of the hot weather
and to flourish during winter:—

Spongilla carteri.

Sponging alba.

Spongilla alba var. bengalensis.

Spongilla crassissima.

Hydra vulgaris.

Victorella bengalensis.

Plumatella fruticosa.

Plumatella emarginata.

Plumatella javanica.

The following forms flourish mainly during the "rains":—

Spongilla lacustris subsp.
reticulata.

Trochospongilla latouchiana.

Trochospongilla phillottiana.

Stolella indica.

The following flourish throughout the year:—

Spongilla proliferens.

Hislopia lacustris.

It is particularly interesting to note that three of the species that
flourish in the mild winter of Bengal, namely Hydra vulgaris,
Plumatella emarginata, and P. fruticosa, are identical
with species that in Europe perish in winter. There is evidence,
moreover, that the statoblasts of the genus to which two of them belong
burst more readily, and thus give rise to new colonies, after being
subjected to a considerable amount of cold. In Bengal they only burst
after being subjected to the heat of the hot weather. Does extreme heat
have a similar effect on aquatic organisms as extreme cold? There is
some evidence that it has.

The species that flourish in India during the rains are all forms
which habitually live near the surface or the edge of ponds or puddles,
and are therefore liable to undergo desiccation as soon as the rains
cease and the cold weather supervenes.

The two species that flourish all the year round do not, properly
speaking, belong to one category, for whereas Hislopia
lacustris[Pg
5] produces no form of resting reproductive body but bears
eggs and spermatozoa at all seasons, Spongilla proliferens is a
short-lived organism that undergoes a biological crisis every few weeks;
that is to say, it begins to develop gemmules as soon as it is fully
formed, and apparently dies down as soon as the gemmules have attained
maturity. The gemmules apparently lie dormant for some little time, but
incessant reproduction is carried on by means of external buds, a very
rare method of reproduction among the freshwater sponges.

The facts just stated prove that considerable specific idiosyncrasy
exists as regards the biology of the sponges, hydroids, and polyzoa of
stagnant water in Bengal; but an even more striking instance of this
phenomenon is afforded by the sponges Spongilla bombayensis and
Corvospongilla lapidosa in Bombay. These two sponges resemble one
another considerably as regards their mode of growth, and are found
together on the lower surface of stones. In the month of November,
however, C. lapidosa is in full vegetative vigour, while C.
bombayensis, in absolutely identical conditions, is already reduced
to a mass of gemmules, having flourished during the "rains." It is thus
clear that the effect of environment is not identical in different
species. This is more evident as regards the groups of animals under
consideration in India (and therefore probably in other tropical
countries) than it is in Europe. The subject is one well worthy of study
elsewhere than in India, for it is significant that specimens of S.
bombayensis taken in November in S. Africa were in a state of
activity, thus contrasting strongly with specimens taken at the same
time of year (though not at the same season from a climatic point of
view) in the Bombay Presidency.

Geographical Distribution of
the Indian Species.

The geographical distribution of the lower invertebrates of fresh and
of stagnant water is often an extremely wide one, probably because the
individual of many species exists at certain seasons or in certain
circumstances in a form that is not only resistant to unfavourable
environment, but also eminently capable of being transported by wind or
currents. We therefore find that some genera and even species are
practically cosmopolitan in their range, while others, so far as our
knowledge goes, appear to have an extraordinarily discontinuous
distribution. The latter[Pg 6] phenomenon may be due solely to our
ignorance of the occurrence of obscure genera or species in localities
in which they have not been properly sought for, or it may have some
real significance as indicating that certain forms cannot always
increase and multiply even in those localities that appear most suitable
for them. As an example of universally distributed species we may take
the European polyzoa of the genus Plumatella that occur in India,
while of species whose range is apparently discontinuous better examples
could not be found than the sponges Trochospongilla pennsylvanica
and Spongilla crateriformis, both of which are only known from N.
America, the British Isles, and India.

My geographical list of the species of sponges, cœlenterates,
and polyzoa as yet found in fresh water in India is modelled on Col.
Alcock's recently published list of the freshwater crabs (Potamonidæ) of
the Indian Empire^[B]. I follow him in
accepting, with slight modifications of my own, Blanford's
physiographical rather than his zoogeographical regions, not because I
think that the latter have been or ought to be superseded so far as the
vertebrates are concerned, but rather because the limits of the
geographical distribution of aquatic invertebrates appear to depend on
different factors from those that affect terrestrial animals or even
aquatic vertebrates.

"Varieties" are ignored in this list, because they are not considered
to have a geographical significance. The parts of India that are least
known as regards the freshwater representatives of the groups under
consideration are the valley of the Indus, the lakes of Kashmir and
other parts of the Himalayas, the centre of the Peninsula, and the basin
of the Brahmaputra. Those that are best known are the districts round
Bombay, Calcutta, Madras and Bangalore, Travancore and Northern
Tenasserim. Little is known as regards Ceylon, and almost nothing as
regards the countries that surround the Indian Empire, a few species
only having been recorded from Yunnan and the Malay Peninsula, none from
Persia, Afghanistan, or Eastern Turkestan, and only one from Tibet.
Professor Max Weber's researches have, however, taught us something as
regards Sumatra and Java, while the results of various expeditions to
Tropical Africa are beginning to cast light on the lower invertebrates
of the great lakes in the centre of that continent and of the basin of
the Nile.

[Pg
7]It is not known to what altitude the three groups range in
the Himalayas and the hills of Southern India. No sponge has been found
in Indian territory at an altitude higher than that of Bhim Tal in
Kumaon (4,500 feet), and Hydra is only known from the plains; but
a variety of H. oligactis was taken by Capt. F. H. Stewart in
Tibet at an altitude of about 15,000 feet. Plumatella diffusa
flourishes at Gangtok in Sikhim (6,100 feet), and I have found
statoblasts of P. fruticosa in the neighbourhood of Simla on the
surface of a pond situated at an altitude of about 8,000 feet; Mr. R.
Kirkpatrick obtained specimens of the genus in the Botanical Gardens at
Darjiling (6,900 feet), and two species have been found at Kurseong
(4,500-5,000 feet) in the same district.

GEOGRAPHICAL LIST OF THE FRESHWATER SPONGES,
HYDROIDS, AND POLYZOA OF INDIA, BURMA, AND CEYLON.

[A * indicates that a species or subspecies has
only been found in one physiographical region or subregion so far as the
Indian Empire is concerned; a † that the species has also been
found in Europe, a § in North America, a in Africa, and a
ʘ in the Malay Archipelago.]

1. Western Frontier Territory^[C].

(Baluchistan, the Punjab, and the N.W. Frontier
Province.)

Sponges:—

1. Spongilla (Eunapius)
carteri†ʘ (Lahore).

Hydroids:—

1. Hydra oligactis†§ (Lahore).

Polyzoa:—

1. Plumatella fruticosa†§
(Lahore).

2. Plumatella diffusa†§
(Lahore).

2. Western Himalayan Territory.

(Himalayas from Hazara eastwards as far as Nepal.)

Sponges:—

1. Spongilla (Eunapius)
carteri†ʘ (Bhim Tal).

2. Ephydatia meyeniʘ (Bhim Tal).

Hydroids:—None known (Hydra
oligactis recorded from Tibet).

Polyzoa:—

1. Plumatella allmani† (Bhim Tal).

2. Plumatella fruticosa†§
(Simla).

3. Lophopodella carteri (Bhim
Tal).

3. North-Eastern Frontier Territory.[Pg 8]

(Sikhim, Darjiling and Bhutan, and the Lower Brahmaputra
Drainage-System.)

Sponges:—

Spongilla proliferensʘ (Assam).

Hydroids:—None known.

Polyzoa:—

1. Plumatella fruticosa† (Kurseong and
Assam).

2. Plumatella diffusa†§
(Sikhim).

3. Plumatella javanicaʘ (Kurseong).

4. Burma Territory.

(Upper Burma, Arrakan, Pegu, Tenasserim.)

Sponges:—

1. Spongilla (Euspongilla)
proliferensʘ (Upper Burma, Pegu).

2. Spongilla (Euspongilla)
crateriformis†§ (Tenasserim).

3. Spongilla (Eunapius)
carteri†ʘ (Upper Burma, Pegu, Tenasserim).

4. Trochospongilla latouchiana
(Tenasserim).

5. Trochospongilla phillottiana
(Tenasserim).

6. Tubella vesparioides* (Tenasserim).

7. Corvospongilla burmanica* (Pegu).

Hydroids:—

1. Hydra vulgaris†§ (Upper Burma
and Tenasserim).

Polyzoa:—

1. Plumatella emarginata†§ (Pegu,
Upper Burma).

2. Plumatella allmani†
(Tenasserim).

3. Pectinatella burmanica (Tenasserim).

4. Hislopia lacustris (Pegu).

5 a. Peninsular Province—Main
Area.

(The Peninsula east of the Western Ghats.)

Sponges:—

1. Spongilla (Euspongilla)
lacustris subsp. reticulata (Orissa, Madras).

2. Spongilla (Euspongilla)
proliferensʘ (Madras).

3. Spongilla (Euspongilla)
alba (N. Madras, Orissa, Hyderabad).

4. Spongilla (Euspongilla)
hemephydatia* (Orissa).

5. Spongilla (Euspongilla)
crateriformis†§.

6. Spongilla (Eunapius)
carteri†ʘ.

7. Spongilla (Eunapius) gemina*
(Bangalore).

8. Spongilla (Stratospongilla)
bombayensis (Mysore).

9. Dosilia plumosa (N. Madras).

Hydroids:—

1. Hydra vulgaris†§.

Polyzoa:—

1. Plumatella fruticosa† (Madras,
Bangalore).

2. Lophopus (?Lophopodella), sp.
(Madras).

3. Pectinatella burmanica (Orissa).

4. Victorella bengalensis (Madras).

5. Hislopia lacustris (Nagpur).

5b. Peninsular Province—Malabar
Zone.[Pg
9]

(Western Ghats from Tapti R. to Cape Comorin and
eastwards to the sea.)

Sponges:—

1. Spongilla (Euspongilla)
lacustris subsp. reticulata (W. Ghats).

2. Spongilla (Euspongilla)
proliferensʘ (Cochin).

3. Spongilla (Euspongilla)
alba.

4. Spongilla (Euspongilla)
cinerea*.

5. Spongilla (Euspongilla)
travancorica* (Travancore).

6. Spongilla (Euspongilla)
crateriformis†§ (Cochin).

7. Spongilla (Eunapius)
carteri†ʘ.

8. Spongilla (Stratospongilla)
indica* (W. Ghats).

9. Spongilla (Stratospongilla)
bombayensis (Bombay, W. Ghats).

10. Spongilla (Stratospongilla)
ultima* (Travancore).

11. Pectispongilla aurea* (Travancore,
Cochin).

12. Ephydatia meyeniʘ (Bombay,
Travancore).

13. Dosilia plumosa (Bombay).

14. Trochospongilla
pennsylvanica*†§ (Travancore).

15. Corvospongilla lapidosa* (W. Ghats).

Hydroids:—None recorded.

Polyzoa:—

1. Fredericella indica* (W. Ghats and
Travancore).

2. Plumatella fruticosa† (Bombay).

3. Plumatella javanicaʘ
(Travancore).

4. Plumatella tanganyikæ* (W.
Ghats).

5. Lophopodella carteri (Bombay, W.
Ghats).

6. Indo-Gangetic Plain.

(From Sind to the Brahmaputra.)

Sponges:—

1. Spongilla (Euspongilla)
lacustris subsp. reticulata (Gangetic delta).

2. Spongilla (Euspongilla)
proliferensʘ (Lower Bengal, etc.).

3. Spongilla (Euspongilla)
alba (Lower Bengal).

4. Spongilla (Euspongilla)
crateriformis†§.

5. Spongilla (Eunapius)
carteri†ʘ (Lower Bengal, etc.).

6. Spongilla (Eunapius)
fragilis subsp. calcuttana* (Lower Bengal).

7. Spongilla (Eunapius)
crassissima (Bengal).

8. Ephydatia meyeniʘ (Lower Bengal).

9. Trochospongilla latouchiana (Lower
Bengal).

10. Trochospongilla phillottiana (Lower
Bengal).

Hydroids:—

1. Hydra vulgaris†§.

Polyzoa:—

1. Plumatella fruticosa†.

2. Plumatella emarginata†§.

3. Plumatella javanicaʘ (Lower
Bengal).

4. Plumatella diffusa†§.

5. Plumatella allmani†.

6. Plumatella punctata†§ (Lower
Bengal).

7. Stolella indica* (Lower Bengal, United
Provinces).

8. Victorella bengalensis (Lower Bengal).

9. Hislopia lacustris (United Provinces, N.
Bengal).

9a. Hislopia lacustris subsp.
moniliformis* (Lower Bengal).

[Pg 10]7. Ceylon.

Sponges:—

1. Spongilla (Euspongilla)
proliferensʘ.

2. Spongilla (Eunapius)
carteri†ʘ.

Hydroids:—

1. Hydra vulgaris†§.

Polyzoa:—

1. ? Plumatella emarginata†§.

2. Pectinatella burmanica.

The most striking feature of this list is the evidence it affords as
to the distinct character of the fauna of the Malabar Zone, a feature
that is also remarkably clear as regards the Potamonidæ, one genus of
which (Gecarcinucus) is peculiar, so far as India is concerned,
to that zone. As regards the sponges we may note the occurrence of no
less than three species of the subgenus Stratospongilla, which
has not been found elsewhere in India except on one occasion in Mysore,
and of a species of the genus Corvospongilla, which is unknown
from the rest of Peninsular India and from the Himalayas. The genus
Pectispongilla is only known from the Malabar Zone. Among the
polyzoa the genus Fredericella^[D] appears to be confined, so far as
the Indian and Burmese fauna is concerned, to the Malabar Zone, and the
same is true as regards the group of species to which Plumatella
tanganyikæ, an African form, belongs.

A further examination of the list of Malabar species and a
consideration of allied forms shows that the majority of the forms
restricted to the Malabar Zone are either African or else closely allied
to African forms. The genus Corvospongilla, except for one
Burmese species, is otherwise peculiar to Tropical Africa; while
Stratospongilla, although not confined to Africa, is more
prolific in species in that continent than in any other. Spongilla
(Stratospongilla) bombayensis has only been found in Bombay, the
Western Ghats, Mysore, and Natal, and Plumatella tanganyikæ only
in the Western Ghats and Central Africa. The genus Fredericella
(which also occurs in Europe, N. America, and Australia) is apparently
of wide distribution in Africa, while Lophopodella (which in
India is not confined to the Malabar Zone) is, except for a Japanese
race of the Indian species, restricted outside India, so far as we know,
to East Africa.

[Pg
11] A less definite relationship between the sponges and
polyzoa of the Malabar Zone and those of countries to the east of India
is suggested by the following facts:—

(1) The occurrence of the genus
Corvospongilla in Burma;


(2) the occurrence of the subgenus Stratospongilla in Sumatra,
China, and the Philippines;


(3) the occurrence of a race of Lophopodella carteri in Japan;


(4) the occurrence of a species allied to Plumatella tanganyikæ
in the Philippines.

It will be noted that in each of these instances the relationship
extends to Africa as well as to the Eastern countries, and is more
marked in the former direction. The species of Stratospongilla,
moreover, that occurs in Sumatra (S. sumatrensis) also occurs in
Africa, while those that have been found in China and the Philippines
are aberrant forms.

At first sight it might appear that these extra-Indian relationships
might be explained by supposing that gemmules and statoblasts were
brought to the Malabar Coast from Africa by the aërial currents of the
monsoon or by marine currents and carried from India eastwards by the
same agency, this agency being insufficient to transport them to the
interior and the eastern parts of the Peninsula. The work of La Touche^[E] on wind-borne foraminifera in
Rajputana is very suggestive in this direction; but that the peculiar
sponge and polyzoon fauna of Malabar is due to the agency either of wind
or of marine currents may be denied with confidence, for it is a
striking fact that most of the characteristic genera and subgenera of
the Zone have resting reproductive bodies that are either fixed to solid
objects or else are devoid of special apparatus to render them light.
The former is the case as regards all species of Corvospongilla
and all Indian and most other species of Stratospongilla, the
gemmules of which not only are unusually heavy but also adhere firmly;
while the statoblasts of Fredericella have no trace of the
air-cells that render the free statoblasts of all other genera of
phylactolæmatous polyzoa peculiarly light and therefore peculiarly
liable to be transported by wind.

[Pg
12]A true geographical or geological explanation must therefore be
sought for the relationship between the sponges and polyzoa of Malabar,
of Africa, and of the Eastern countries—a relationship that is
well known to exist as regards other groups of animals. No more
satisfactory explanation has as yet been put forward than that of a
former land connection between Africa and the Malaysia through Malabar
at a period (probably late Cretaceous) when the Western Ghats were much
higher than they now are^[F].

There is little to be said as regards the distribution of the
sponges, hydroids, and polyzoa of fresh water in other parts of India.
It may be noted, however, that the species known from the Punjab are all
widely distributed Palæarctic forms, and that the genus Stolella
is apparently confined to the Indo-Gangetic Plain. Two species of sponge
are peculiar to Lower Burma, one of them (Corvospongilla
burmanica) representing the geographical alliance already discussed
as regards the Malabar Zone, the other (Tubella vesparioides)
closely related to a Malaysian species (T. vesparium from Borneo)
and perhaps representing the northern limit of the Malaysian element
well known in the fauna of Lower Burma. Of the sponges and polyzoa of
Ceylon we know as yet too little to make it profitable to discuss their
affinities. All that have as yet been discovered occur also in
Peninsular India; nor do they afford any evidence of a connection with
the Malabar Zone.

The question of the geographical range of the sponges, hydroids, and
polyzoa of brackish water may be considered briefly, for it is of
importance in considering that of those which are confined to fresh
water. Some of these species from brackish water (e. g.,
Membranipora lacroixii) are identical with others (e. g.,
Victorella bengalensis and Bowerbankia caudata subsp.
bengalensis) closely related to European forms. Others again
(e. g., Loxosomatoides colonialis and Sagartia
schilleriana) are known as yet from the Ganges delta only. In our
ignorance of the Indian representatives of the groups to which they
belong, it is impossible to assert that their distribution is actually
so restricted as it seems.

[Pg 13]Some Special
Localities.

In order to avoid constant repetition as regards the conditions that
prevail at the places most frequently mentioned in this volume, a few
details as regards them may be conveniently stated here.

Lower Bengal.

Calcutta is situated on the River Hughli
at a point about 90 miles from the open sea. The water of the river is
practically fresh, but is strongly affected by the tides; it is always
turbid and of a brownish colour. The river, however, is not a good
collecting ground for sponges, cœlenterates, and polyzoa, and none
of the species described in this volume have been obtained from it. It
is in the Calcutta "tanks" that most of my investigations have been
made. These tanks are ponds, mostly of artificial origin, very numerous,
of varying size but never very large or deep. Most of them contain few
solid objects to which sedentary organisms can fix themselves, and such
ponds are of course poor in sponges and polyzoa. Others, however,
support a prolific growth of weeds such as Pistia stratiotes,
Lemna, and Limnanthemum, and a few have brickwork or
artificial stonework at their sides. In those parts of the town that
approach the Salt Lakes (large lagoons and swamps of brackish water
connected with the sea by the Mutlah River) the water of the ponds is
slightly brackish and permits few plants except algæ to flourish. Few of
the bigger tanks ever dry up. The best of the tanks from the
sponge-collector's point of view, so far as I have been able to
discover, is the one in the compound of the Indian Museum. It enjoys all
the advantages of light and shade, solid supports, prolific aquatic
vegetation, considerable depth, and the vicinity of human dwellings that
seem to be favourable to the growth of sponges, no less than nine
species of which, representing three genera and two subgenera, grow
abundantly in it. Hydra also flourishes in this pond, but for
some reasons there are few polyzoa. The phylactolæmatous species of the
latter group, however, are extraordinarily abundant in one of the tanks
in the Zoological Gardens at Alipore. In this tank, which unlike the
Museum tank is directly connected with the river, no less than six
species and varieties of the genus Plumatella have been found
growing together on sticks, floating seeds, and water-plants. Except
Hislopia, which is common on Vallisneria in one tank on
the[Pg
14] Maidan (opposite the Bengal Club), the ctenostomes of
stagnant water are only found in the tanks near the Salt Lakes.

Port Canning is situated on the Mutlah
River about 30 miles from Calcutta and about 60 from the open sea. The
Mutlah is really a tidal creek rather than a river, in spite of the fact
that it runs for a considerable number of miles, and its waters are
distinctly brackish. Water taken from the edge at Port Canning in March
was found to contain 25.46 per thousand of saline residue. The
interesting feature of Port Canning, however, is from a zoological point
of view not the Mutlah but certain ponds of brackish water now
completely separated from it, except occasionally when the river is in
flood, but communicating regularly with it in the memory of living
persons. These ponds, which were apparently not in existence in 1855,
have on an average an area of about half an acre each, and were
evidently formed by the excavation of earth for the construction of an
embankment along the Mutlah. They are very shallow and lie exposed to
the sun. The salinity differs considerably in different ponds, although
the fauna seems to be identical; the water of one pond was found to
contain 22.88 per thousand of saline residue in May, 20.22 per thousand
in March, and 12.13 in December. A second pond in the neighbourhood of
the first and apparently similar to it in every way contained only 9.82
per thousand in July, after the rains had broken. The fauna of these
ponds includes not only a freshwater sponge (Spongilla alba var.
bengalensis) but also many aquatic insects (e. g.,
larvæ of mosquitos and of Chironomus and several species of
beetles and Rhynchota); while on the other hand essentially marine
cœlenterates (Irene ceylonensis, etc.) and worms
(e. g., the gephyrean Physcosoma lurco^[G]) form a part of it, together with
forms of intermediate habitat such as Bowerbankia caudata subsp.
bengalensis, Victorella bengalensis, and several fish and
crustacea common in brackish water.

Orissa.

Orissa may be described in general terms as consisting of the coastal
area of Bengal south of the Gangetic delta. It extends in inland,
however, for a considerable distance and includes hilly tracts. There is
no geographical boundary between it and the[Pg 15] north-eastern part of the
Madras Presidency or the eastern part of the Central Provinces.

Chilka Lake.—This marine lake is a
shallow lagoon measuring about 40 miles in length and 10 miles in
breadth, and formed in geologically recent times by the growth of a
narrow sand-bank across the mouth of a wide bay. At its northern end it
communicates with the sea by a narrow channel, and throughout its length
it is strongly affected by the tides. At its south end, which is
actually situated in the Ganjam district of Madras, the water is
distinctly brackish and is said to be nearly fresh at certain times of
year. At this end there are numerous small artificial pools of brackish
water somewhat resembling those of Port Canning as regards their
fauna.

Sur (or Sar)
Lake.—A shallow, freshwater lake of
very variable size situated a few miles north of Puri on the Orissa
coast. In origin it probably resembled the Chilka Lake, but it is now
separated from the sea by about 3 miles of barren sand dunes, among
which numerous little pools of rain-water are formed during the rains.
These dry up completely in winter, and even the lake itself is said
sometimes almost to disappear, although when it is full it is several
miles in length. The fauna is essentially a freshwater one, but includes
certain Mysidæ and other crustacea usually found in brackish water.

Bombay Presidency.

Bombay.—The town of Bombay, built on
an island near the mainland, is situated close to swamps and creeks of
brackish water not unlike those that surround Calcutta. Its "tanks,"
however, differ from those of Calcutta in having rocky bottoms and, in
many cases, in drying up completely in the hot weather. Of the fauna of
the swamps extremely little is known, but so far as the sponges and
polyzoa of the tanks are concerned the work undertaken by Carter was
probably exhaustive.

Igatpuri.—Igatpuri is situated at an
altitude of about 2000 feet, 60 miles north-east of Bombay. Above the
town there is a lake of several square miles in area whence the
water-supply of several stations in the neighbourhood is obtained. The
water is therefore kept free from contamination. The bottom is composed
of small stones and slopes gradually up at the edges. During the dry
weather its level sinks considerably. Several interesting sponges[Pg 16] and
polyzoa have been found in this lake, most of them also occurring in a
small pond in the neighbourhood in which clothes are washed and the
water is often full of soap-suds.

Southern India.

Madras.—The city of Madras is built
by the sea, straggling over a large area of the sandy soil
characteristic of the greater part of the east coast of India. In wet
weather this soil retains many temporary pools of rain-water, and there
are numerous permanent tanks of no great size in the neighbourhood of
the town. The so-called Cooum River, which flows through the town, is
little more than a tidal creek, resembling the Mutlah River of Lower
Bengal on a much smaller scale. The sponges and polyzoa as yet found in
the environs of Madras are identical with those found in the environs of
Calcutta.

Bangalore.—Bangalore (Mysore State)
is situated near the centre of the Madras Presidency on a plateau about
3000 feet above sea-level. The surrounding country is formed of laterite
rock which decomposes readily and forms a fine reddish silt in the
tanks. These tanks are numerous, often of large size, and as a rule at
least partly of artificial origin. Their water supports few phanerogamic
plants and is, as my friend Dr. Morris Travers informs me, remarkably
free from salts in solution. The sponge fauna of the neighbourhood of
Bangalore appears to be intermediate between that of Madras and that of
Travancore.

The Backwaters of Cochin and
Travancore.—The "backwaters" of Cochin and Travancore were
originally a series of shallow lagoons stretching along the coast of the
southern part of the west coast of India for a distance of considerably
over a hundred miles. They have now been joined together by means of
canals and tunnels to form a tidal waterway, which communicates at many
points directly with the sea. The salinity of the water differs greatly
at different places and in different seasons, and at some places there
is an arrangement to keep out sea-water while the rice-fields are being
irrigated. The fauna is mainly marine, but in the less saline parts of
the canals and lakes many freshwater species are found.

Shasthancottah.—There are two villages of this name, one
situated on the backwater near Quilon (coast of Travancore), the[Pg 17] other
about three miles inland on a large freshwater lake. This lake, which
does not communicate with the backwater, occupies a narrow winding rift
several miles in length at a considerable depth below the surrounding
country. Its bottom is muddy and it contains few water-plants, although
in some places the water-plants that do exist are matted together to
form floating islands on which trees and bushes grow. The fauna, at any
rate as regards mollusca and microscopic organisms, is remarkably poor,
but two species of polyzoa (Fredericella indica and Plumatella
fruticosa) and one of sponge (Trochospongilla pennsylvanica)
grow in considerable abundance although not in great luxuriance.

The Himalayas.

Bhim Tal^[H] is a lake situated at an altitude of
4500 feet in that part of the Western Himalayas known as Kumaon, near
the plains. It has a superficial area of several square miles, and is
deep in the middle. Its bottom and banks are for the most part muddy.
Little is known of its fauna, but two polyzoa (Plumatella allmani
and Lophopodella carteri) and the gemmules of two sponges
(Spongilla carteri and Ephydatia meyeni) have been found
in it.

* * * * *

Nomenclature and
Terminology.

The subject of nomenclature may be considered under four
heads:—(I.) the general terminology of the various kinds of groups
of individuals into which organisms must be divided; (II.) the general
nomenclature of specimens belonging to particular categories, such as
types, co-types, etc.; (III.) the nomenclature that depends on such
questions as that of "priority"; and (IV.) the special terminology
peculiar to the different groups. The special terminology peculiar to
the different groups is dealt with in the separate introductions to each
of the three parts of this volume.

(I.)

No group of animals offers greater difficulty than the sponges,
hydroids, and polyzoa (and especially the freshwater representatives of
these three groups) as regards the question "What is a species?" and the
kindred questions, "What is a subspecies?" "What is a variety?" and
"What is a phase?" Genera can[Pg 18] often be left to look after themselves,
but the specific and kindred questions are answered in so many different
ways, if they are even considered, by different systematists, especially
as regards the groups described in this volume, that I feel it necessary
to state concisely my own answers to these questions, not for the
guidance of other zoologists but merely to render intelligible the
system of classification here adopted. The following definitions should
therefore be considered in estimating the value of "species," etc.,
referred to in the following pages.

Species.—A group of individuals differing in constant
characters of a definite nature and of systematic^[I] importance from all others in the
same genus.

Subspecies.—An isolated or local race, the individuals
of which differ from others included in the same species in characters
that are constant but either somewhat indefinite or else of little
systematic importance.

Variety.—A group of individuals not isolated
geographically from others of the same species but nevertheless
exhibiting slight, not altogether constant, or indefinite differences
from the typical form of the species (i. e., the form first
described).

Phase.—A peculiar form assumed by the individuals of a
species which are exposed to peculiarities in environment and differ
from normal individuals as a direct result.

There are cases in which imperfection of information renders it
difficult or impossible to distinguish between a variety and a
subspecies. In such cases it is best to call the form a variety, for
this term does not imply any special knowledge as regards its
distribution or the conditions in which it is found.

I use the term "form" in a general sense of which the meaning or
meanings are clear without explanation.

(II.)

The question of type specimens must be considered briefly. There are
two schools of systematists, those who assert that one specimen and one
only must be the type of a species, and those who are willing to accept
several specimens as types. From the theoretical point of view it seems
impossible to set up any one[Pg 19] individual as the ideal type of a
species, but those who possess collections or are in charge of museums
prefer, with the natural instinct of the collector, to have a definite
single type (of which no one else can possibly possess a duplicate) in
their possession or care, and there is always the difficulty that a
zoologist in describing a species, if he recognizes more than one type,
may include as types specimens that really belong to more than one
species. These difficulties are met by some zoologists by the
recognition of several specimens as paratypes, all of equal value; but
this, after all, is merely a terminological means of escaping from the
difficulty, calculated to salve the conscience of a collector who feels
unwilling to give up the unique type of a species represented by other
specimens in his collection. The difficulty as regards the confounding
of specimens of two or more species as the types of one can always be
adjusted if the author who discovers the mistake redescribes one of the
species under the original name and regards the specimen that agrees
with his description as the type, at the same time describing a new
species with another of the specimens as its type. Personally I always
desire to regard the whole material that forms the basis of an original
description of a species as the type, but museum rules often render this
impossible, and the best that can be done is to pick out one specimen
that seems particularly characteristic and to call it the type, the rest
of the material being termed co-types. A peculiar difficulty arises,
however, as regards many of the sponges, cœlenterates, and
polyzoa, owing to the fact that they are often either compound animals,
each specimen consisting of more than one individual, or are easily
divisible into equivalent fragments. If the single type theory were
driven to its logical conclusion, it would be necessary to select one
particular polyp in a hydroid colony, or even the part of a sponge that
surrounded a particular osculum as the type of the species to which the
hydroid or the sponge belonged. Either by accident or by design
specimens of Spongillidæ, especially if kept dry, are usually broken
into several pieces. There is, as a matter of fact, no reason to
attribute the peculiarly sacrosanct nature of a type to one piece more
than another. In such cases the biggest piece may be called the type,
while the smaller pieces may be designated by the term "schizotype."

The more precise definition of such terms as topotype, genotype,
et hujus generis omnis is nowadays a science (or at any rate a
form of technical industry) by itself and need not be discussed
here.

[Pg 20](III.)

In 1908 an influential committee of British zoologists drew up a
strenuous protest against the unearthing of obsolete zoological names
(see 'Nature,' Aug. 1908, p. 395). To no group does this protest apply
with greater force than to the three discussed in this volume. It is
difficult, however, to adopt any one work as a standard of nomenclature
for the whole of any one of them. As regards the Spongillidæ it is
impossible to accept any monograph earlier than Potts's "Fresh-Water
Sponges" (P. Ac. Philad., 1887), for Bowerbank's and Carter's earlier
monographs contained descriptions of comparatively few species. Even
Potts's monograph I have been unable to follow without divergence, for
it seems to me necessary to recognize several genera and subgenera that
he ignored. The freshwater polyzoa, however, were dealt with in so
comprehensive a manner by Allman in his "Fresh-Water Polyzoa" (London,
1856) that no difficulty is experienced in ignoring, so far as
nomenclature is concerned, any earlier work on the group; while as
regards other divisions of the polyzoa I have followed Hincks's "British
Marine Polyzoa" (1880), so far as recent researches permit. In most
cases I have not attempted to work out an elaborate synonymy of species
described earlier than the publication of the works just cited, for to
do so is a mere waste of time in the case of animals that call for a
most precise definition of species and genera and yet were often
described, so far as they were known earlier than the dates in question,
in quite general terms. I have been confirmed in adopting this course by
the fact that few of the types of the earlier species are now in
existence, and that a large proportion of the Indian forms have only
been described within the last few years.

Material.

The descriptions in this volume are based on specimens in the
collection of the Indian Museum, the Trustees of which, by the liberal
manner in which they have permitted me to travel in India and Burma on
behalf of the Museum, have made it possible not only to obtain material
for study and exchange but also to observe the different species in
their natural environment. This does not mean to say that specimens from
other collections have been ignored, for many institutions and
individuals have met us generously in the matter of gifts and exchanges,
and our collection[Pg 21] now includes specimens of all the
Indian forms, named in nearly all cases by the author of the species,
except in those of species described long ago of which no authentic
original specimens can now be traced. Pieces of the types of all of the
Indian Spongillidæ described by Carter have been obtained from the
British Museum through the kind offices of Mr. R. Kirkpatrick. The
Smithsonian Institution has sent us from the collection of the United
States National Museum specimens named by Potts, and the Berlin Museum
specimens named by Weltner, while to the Imperial Academy of Sciences of
St. Petersburg we owe many unnamed but interesting sponges. Dr. K.
Kraepelin and Dr. W. Michaelsen have presented us with specimens of most
of the species and varieties of freshwater polyzoa described by the
former in his great monograph and elsewhere. We owe to Dr. S. F. Harmer,
formerly of the Cambridge University Museum and now Keeper in Zoology at
the British Museum, to Professor Max Weber of Amsterdam, Professor Oka
of Tokyo, and several other zoologists much valuable material. I would
specially mention the exquisite preparations presented by Mr. C.
Rousselet. Several naturalists in India have also done good service to
the Museum by presenting specimens of the three groups described in this
volume, especially Major H. J. Walton, I.M.S., Major J. Stephenson,
I.M.S., Dr. J. R. Henderson and Mr. G. Matthai of Madras, and Mr. R.
Shunkara Narayana Pillay of Trivandrum.

The following list shows where the types of the various species,
subspecies, and varieties are preserved, so far as it has been possible
to trace them. I have included in this list the names of all species
that have been found in stagnant water, whether fresh or brackish, but
those of species not yet found in fresh water are enclosed in square
brackets.

[Pg
22]

The literature dealing with the various groups described in
the volume is discussed in the introductions to the three parts.
Throughout the volume I have, so far as possible, referred to works that
can be consulted in Calcutta in the libraries of the Indian Museum, the
Geological Survey of India, or the Asiatic Society of Bengal. The names
of works that are not to be found in India are marked with a *. The
rarity with which this mark occurs says much for the fortunate position
in which zoologists stationed in Calcutta find themselves as regards
zoological literature, for I do not think that anything essential has
been omitted.

It remains for me to express my gratitude to those who have assisted
me in the preparation of this volume. The names of[Pg 24] those
who have contributed specimens for examination have already been
mentioned. I have to thank the Trustees of the Indian Museum not only
for their liberal interpretation of my duties as an officer of the
Museum but also for the use of all the drawings and photographs and some
of the blocks from which this volume is illustrated. Several of the
latter have already been used in the "Records of the Indian Museum."
From the Editor of the "Fauna" I have received valuable suggestions, and
I am indebted to Dr. Weltner of the Berlin Museum for no less valuable
references to literature. Mr. F. H. Gravely, Assistant Superintendent in
the Indian Museum, has saved me from several errors by his
criticism.

The majority of the figures have been drawn by the draftsmen of the
Indian Museum, Babu Abhoya Charan Chowdhary, and of the Marine Survey of
India, Babu Shib Chandra Mondul, to both of whom I am much indebted for
their accuracy of delineation.

No work dealing with the sponges of India would be complete without a
tribute to the memory of H. J. Carter, pioneer in the East of the study
of lower invertebrates, whose work persists as a guide and an
encouragement to all of us who are of the opinion that biological
research on Indian animals can only be undertaken in India, and that
even systematic zoological work can be carried out in that country with
success. I can only hope that this, the first volume in the official
Fauna of the Indian Empire to be written entirely in India, may prove
not unworthy of his example.

Indian Museum, Calcutta 
Oct. 23rd, 1910.

[A] "L'origine des animaux d'eau douce," Bull.
de l'Acad. roy. de Belgique (Classe des Sciences), No. 12, 1905, p.
724.

[B] Cat. Ind. Dec. Crust. Coll. Ind. Mus.,
part i, fasc. ii (Potamonidæ), 1910.

[C] I include Baluchistan in this territory
largely for climatic reasons.

[D] Mr. S. W. Kemp recently obtained at
Mangaldai, near the Bhutan frontier of Assam, a single specimen of what
may be a species of Fredericella.

[E] See Mem. Geol. Surv. Ind. xxxv (1), p. 39 (1902).

[F] See Ortmann, "The Geographical
Distribution of Freshwater Decapods and its bearing upon Ancient
Geography," Proc. Amer. Phil. Soc. xli, p. 380, fig. 6 (1902); also
Suess, "The Face of the Earth" (English ed.) i, p. 416 (1904).

[G] I am indebted to Mr. W. F. Lanchester for
the identification of this species.

[H] The fauna of this lake and of others in
the neighbourhood has recently been investigated by Mr. S. W. Kemp. See
the addenda at the end of this volume.—June 1911.

[I] "What characters are of systematic
importance?" is a question to which different answers must be given in
the case of different groups.

[J] I have failed to obtain from the
Philadelphia Academy of Science a statement that the type of this
species is still in existence.

[Pg
25]

PART I.

FRESHWATER SPONGES

(SPONGILLIDÆ).

[Pg
26]
[Pg 27]

INTRODUCTION TO PART I.

I.

The Phylum Porifera.

The phylum Porifera or Spongiæ includes the simplest of the Metazoa
or multicellular animals. From the compound Protozoa its members are
distinguished by the fact that the cells of which they are composed
exhibit considerable differentiation both in structure and in function,
and are associated together in a definite manner, although they are not
combined to form organs and systems of organs as in the higher Metazoa.
Digestion, for instance, is performed in the sponges entirely by
individual cells, into the substance of which the food is taken, and the
products of digestion are handed on to other cells without the
intervention of an alimentary canal or a vascular system, while there is
no structure in any way comparable to the nervous system of more highly
organized animals.

The simplest form of sponge, which is known as an olynthus, is a
hollow vase-like body fixed at one end to some solid object, and with an
opening called the osculum at the other. The walls are perforated by
small holes, the pores, from which the name Porifera is derived.

Externally the surface is protected by a delicate membrane formed of
flattened cells and pierced by the pores, while the interior of the vase
is covered with curious cells characteristic of the sponges, and known
as choanocytes or collar-cells. They consist of minute oval or
pear-shaped bodies, one end of which is provided with a rim or collar of
apparently structureless membrane, while a flagellum or whip-like lash
projects from the centre of the surface surrounded by the collar. These
collar-cells are practically identical with those of which the Protozoa
known as Choanoflagellata consist; but it is only in the sponges^[K] that they are found constantly
associated with other cells unlike themselves.

In addition to the collar-cells, which form what is called the
gastral layer, and the external membrane (the derma or dermal[Pg 28]
membrane), the sponge contains cells of various kinds embedded in a
structureless gelatinous substance, through which they have the power of
free movement. Most of these cells have also the power of changing their
form in an "amœboid" manner; that is to say, by projecting and
withdrawing from their margin mobile processes of a more or less
finger-like form, but unstable in shape or direction. The protoplasm of
which some of the cells are formed is granular, while that of others is
clear and translucent. Some cells, which (for the time being at any
rate) do not exhibit amœboid movements, are glandular in function,
while others again give rise in various ways to the bodies by means of
which the sponge reproduces its kind. There is evidence, however, that
any one kind of cell, even those of the membrane and the gastral layer,
can change its function and its form in case of necessity.

Most sponges possess a supporting framework or skeleton. In some it
is formed entirely of a horny substance called spongin (as in the
bath-sponge), in others it consists of spicules of inorganic matter
(either calcareous or siliceous) secreted by special cells, or of such
spicules bound together by spongin. Extraneous objects, such as
sand-grains, are frequently included in the skeleton. The spongin is
secreted like the spicules by special cells, but its chemical structure
is much more complicated than that of the spicules, and it is not
secreted (at any rate in most cases) in such a way as to form bodies of
a definite shape. In the so-called horny sponges it resembles the chitin
in which insects and other arthropods are clothed.

* * * * *

In no adult sponge do the collar-cells completely cover the whole of
the internal surface, the olynthus being a larval form, and by no means
a common larval form. It is only found in certain sponges with
calcareous spicules. As the structure of the sponge becomes more
complicated the collar-cells are tucked away into special pockets or
chambers known as ciliated chambers, and finally the approach to these
chambers, both from the external surface and from the inner or gastral
cavity, takes the form of narrow tubes or canals instead of mere pores.
With further complexity the simple internal cavity tends to disappear,
and the sponge proliferates in such a way that more than one osculum is
formed. In the class Demospongiæ, to which the sponges described in this
volume belong, the whole system is extremely complicated.

The skeleton of sponges, when it is not composed wholly of spongin,
consists of, or at any rate contains, spicules that have a definite
chemical composition and definite shapes in accordance with the class,
order, family, genus, and species of the sponge. Formerly sponges were
separated into calcareous, siliceous, and horny sponges by the nature of
their skeleton; and although the system of classification now adopted
has developed into a much more complex one and a few sponges are known
that have both calcareous and siliceous spicules, the question whether
the spicules[Pg
29] are formed of salts of lime or of silica (strictly
speaking of opal) is very important. All Demospongiæ that have spicules
at all have them of the latter substance, and the grade Monaxonida, in
which the freshwater sponges constitute the family Spongillidæ, is
characterized by the possession of spicules that have typically the form
of a needle pointed at both ends. Although spicules of this simple form
may be absent in species that belong to the grade, the larger spicules,
which are called megascleres, have not normally more than one main axis
and are always more or less rod-like in outline. They are usually
arranged so as to form a reticulate skeleton. Frequently, however, the
megascleres or skeleton-spicules are not the only spicules present, for
we find smaller spicules (microscleres) of one or more kinds lying loose
in the substance of the sponge and in the external membrane, or, in the
Spongillidæ only, forming a special armature for the reproductive bodies
known as gemmules.

All sponges obtain their food in the same way, namely by means of the
currents of water set up by the flagella of the collar-cells. These
flagella, although apparently there is little concerted action among
them, cause by their rapid movements changes of pressure in the water
contained in the cavities of the sponge. The water from outside
therefore flows in at the pores and finally makes its way out of the
oscula. With the water minute particles of organic matter are brought
into the sponge, the collar-cells of which, and probably other cells,
have the power of selecting and engulfing suitable particles. Inside the
cells these particles undergo certain chemical changes, and are at least
partially digested. The resulting substances are then handed on directly
to other cells, or, as some assert, are discharged into the common
jelly, whence they are taken up by other cells.

Sponges reproduce their kind in more ways than one, viz., by
means of eggs (which are fertilized as in other animals by spermatozoa),
by means of buds, and by means of the peculiar bodies called gemmules
the structure and origin of which is discussed below (p. 42). They are
of great importance in the classification of the Spongillidæ. Sponges
can also be propagated artificially by means of fission, and it is
probable that this method of reproduction occurs accidentally, if not
normally, in natural circumstances.

General Structure of the
Spongillidæ.

It would be impracticable in this introduction to give a full account
of the structure of the Spongillidæ, which in some respects is still
imperfectly known. Students who desire further information should
consult Professor Minchin's account of the sponges in Lankester's
'Treatise on Zoology,' part ii, or, if a less technical description is
desired, Miss Sollas's contribution to the 'Cambridge Natural History,'
vol. i, in which special attention is paid to Spongilla.

[Pg
30]The diagram reproduced in fig. 1 gives a schematic view of
a vertical section through a living freshwater sponge. Although it
represents the structure of the organism as being very much simpler than
is actually the case, and entirely omits the skeleton, it will be found
useful as indicating the main features of the anatomy.

Fig. 1.—Diagram of a vertical section through a
freshwater sponge
(modified from Kükenthal)

A=pores; B=subdermal cavity; C=inhalent canal;
D=ciliated chamber; E=exhalent canal; F=osculum; G=dermal membrane;
H=eggs; J=gemmule.

It will be noted that the diagram represents an individual with a
single osculum or exhalent aperture. As a rule adult Demospongiæ have
several or many oscula, but even in the Spongillidæ sponges occur in
which there is only one. New oscula are formed by a kind of
proliferation that renders the structure still more complex than it is
when only one exhalent aperture is present.

The little arrows in the figure indicate the direction of the
currents of water that pass through the sponge. It enters through small
holes in the derma into a subdermal cavity, which separates the membrane
from the bulk of the sponge. This space differs greatly in extent in
different species. From the subdermal space the water is forced by the
action of the flagella into narrow tubular canals that carry it into the
ciliated chambers. Thence it passes into other canals, which communicate
with what remains of the central cavity, and so out of the oscula.

The ciliated chambers are very minute, and the collar-cells
excessively so. It is very difficult to examine them owing to their
small size and delicate structure. Fig. 2 D represents a collar-cell of
a sponge seen under a very high power of the microscope in ideal
conditions.

[Pg 31]

Fig. 2.—Sponge cells.

A=bubble-cells of Ephydatia mülleri, × 350
(after Weltner). B=gemmule-cell of Spongilla lacustris
containing green corpuscles (shaded dark), × 800 (after Weltner).
C=gemmule-cell of Ephydatia blembingia showing "tabloids" of
food-material, × 1150 (after Evans). D=collar-cell of
Esperella ægagrophila, × 1600 (after Vosmaer and
Pekelharing). E=three stages in the development of a gemmule-spicule
of E. blembingia (after Evans), × 665. F=outline of
porocytes of S. proliferens, × ca. 1290: e=dermal cell;
n=nucleus; p=pore; p.c.=pore-cell.

The nature of the inhalent apertures in the external membrane has
been much discussed as regards the Demospongiæ, but the truth seems to
be that their structure differs considerably even in [Pg 32]
closely allied species. At any rate this is the case as regards the
Indian Spongillæ. In all species the membrane is composed of
flattened cells of irregular shape fitted together like the pieces of a
puzzle-picture. In some species (e. g., Spongilla carteri)
the apertures in the membrane consist merely of spaces between adjacent
cells, which may be a little more crowded together than is usual. But in
others (e. g., Spongilla proliferens and Spongilla
crassissima) in which the pores are extremely small, each pore
normally pierces the middle of a flat, ring-shaped cell or porocyte.
Occasionally, however, a pore may be found that is enclosed by two
narrow, crescent-shaped cells joined together at their tips to form a
ring. The porocytes of sponges like Spongilla carteri are
probably not actually missing, but instead of being in the external
membrane are situated below the derma at the external entrance to the
canals that carry water to the flagellated chambers or even at the
entrance to the chambers themselves^[L]. Some authors object on theoretical
grounds to the statement that porocytes exist in the Demospongia, and it
is possible that these cells have in this grade neither the same origin
as, nor a precisely similar function to, the porocytes of other sponges.
When they occur in the dermal membrane no great difficulty is
experienced in seeing them under a sufficiently high power of the
microscope, if the material is well preserved and mounted and stained in
a suitable manner^[M]. In most sponges
the porocytes can contract in such a way that the aperture in their
centre is practically closed, but this power appears to be possessed by
the porocytes of Spongilla only to a very limited extent,
although they closely resemble the porocytes of other sponges in
appearance.

The external membrane in many Spongillidæ is prolonged round and
above the oscula so as to form an oscular collar. This structure is
highly contractile, but cannot close together. As a rule it is much more
conspicuous in living sponges than in preserved specimens.

It is not necessary to deal here with most of the cells that occur in
the parenchyma or gelatinous part of the sponge. A full list of the
kinds that are found is given by Dr. Weltner in his
"Spongillidenstudien, V," p. 276 (Arch. Naturg. Berlin, lxxiii (i),
1907). One kind must, however, be briefly noticed as being of some
systematic importance, namely the "bubble-cells" (fig. 2 A) that are
characteristic of some species of Ephydatia and other genera.
These cells are comparatively large, spherical in form; each of them
contains a globule of liquid which not only occupies the greater part of
the cell, but forces the protoplasm to assume the form of a delicate
film lining the cell-wall and covering the[Pg 33] globule. In optical
section "bubble-cells" have a certain resemblance to porocytes, but the
cell is of course imperforate and not flattened.

Skeleton and Spicules.

Radial sections of fragments of the skeletons of
Spongillæ

A, S. crassissima var. crassior (from
Rajshahi); B, S. carteri (from Calcutta); a=transverse,
b=radiating fibres; e=external surface of the sponge.

In the Spongillidæ the spicules and the skeleton are more important
as regards the recognition of genera and species than[Pg 34] the
soft parts. The skeleton is usually reticulate, but sometimes consists
of a mass of spicules almost without arrangement. The amount of spongin
present is also different in different species. The spicules in a
reticulate skeleton are arranged so as to form fibres of two
kinds—radiating fibres, which radiate outwards from the centre of
the sponge and frequently penetrate the external membrane, and
transverse fibres, which run across from one radiating fibre to another.
The fibres are composed of relatively large spicules (megascleres)
arranged parallel to one another, overlapping at the ends, and bound
together by means of a more or less profuse secretion of spongin. In
some species they are actually enclosed in a sheath of this substance.
The radiating fibres are usually more distinct and stouter than the
transverse ones, which are often represented by single spicules but are
sometimes splayed out at the ends so as to assume in outline the form of
an hour-glass (fig. 3 B). The radiating fibres frequently raise up the
membrane at their free extremities just as a tent-pole does a tent.

Normal spicules of the skeleton are always rod-like or needle-like,
and either blunt or pointed at both ends; they are either
smooth, granular, or covered with small spines. Sometimes
spicules of the same type form a more or less irregular transverse
network at the base or on the surface of the sponge.

Fig. 4.—Part of an oscular collar of
Spongilla lacustris subsp. reticulata, showing arrangement
of microscleres in the derma (magnified).

From the systematist's point of view, the structure of the free
spicules found scattered in the substance and membrane of the sponge,
and especially of those that form the armature of the gemmules, is of
more importance than that of the skeleton-spicules. Free spicules are
absent in many species; when present they are usually needle-like and
pointed at the tips. In a few species, however, they are of variable or
irregular form, or consist of several or many shafts meeting in a common
central nodule. In one genus (Corvospongilla) they resemble a
double grappling-iron in form, having a circle of strongly recurved
hooks at both ends. The free microscleres, or flesh-spicules as they are
often called, are either smooth, granular, or spiny.

[Pg
35] Gemmule-spicules, which form a characteristic feature of
the Spongillidæ, are very seldom absent when the gemmules are mature.
They are of the greatest importance in distinguishing the genera. In
their simplest form they closely resemble the free microscleres, but in
several genera they bear, either at or near one end or at or near both
ends, transverse disks which are either smooth or indented round the
edge. In one genus (Pectispongilla) they are provided at both
ends not with disks but with vertically parallel rows of spines
resembling combs in appearance.

The simpler spicules of the Spongillidæ are formed in single cells
(see fig. 2 E), but those of more complicated shape are produced by
several cells acting in concert. Each spicule, although it is formed
mainly of hydrated silica (opal), contains a slender organic filament
running along its main axis inside the silica. This filament, or rather
the tube in which it is contained, is often quite conspicuous, and in
some species (e. g., Spongilla crassissima) its termination
is marked at both ends of the megasclere by a minute conical
protuberance in the silica.

Unless sponges are alchemists and can transmute one element into
another, the material of which the spicules are made must ultimately
come from the water in which the sponges live, or the rocks or other
bodies to or near which they are attached. The amount of water that must
pass through a large specimen of such a sponge as Spongilla
carteri in order that it may obtain materials for its skeleton must
be enormous, for silica is an insoluble substance. I have noticed,
however, that this sponge is particularly abundant and grows with
special luxuriance in ponds in which clothes are washed with soap, and
my friend Mr. G. H. Tipper has suggested to me that possibly the alkali
contained in the soap-suds may assist the sponge in dissolving out the
silica contained in the mud at the bottom of the ponds. The question of
how the mineral matter of the skeleton is obtained is, however, one
about which we know nothing definite.

The spongin that binds the skeleton-spicules together takes the form
of a colourless or yellowish transparent membrane, which is often
practically invisible. When very abundant it sometimes extends across
the nodes of the skeleton as a delicate veil. In some sponges it also
forms a basal membrane in contact with the object to which the sponge is
attached, and in some such cases the spongin of the radiating fibres is
in direct continuity with that of the basal membrane.

Colour and Odour.

Most freshwater sponges have a bad odour, which is more marked in
some species than in others. This odour is not peculiar to the
Spongillidæ, for it is practically identical with that given out by the
common marine sponge Halichondria panicea.[Pg 36] Its
function is probably protective, but how it is produced we do not
know.

The coloration of freshwater sponges is usually dull and uniform, but
Pectispongilla aurea is of the brilliant yellow indicated by its
name, while many species are of the bright green shade characteristic of
chlorophyll, the colouring matter of the leaves of plants. Many species
are brown or grey, and some are almost white.

These colours are due to one of three causes, or to a combination of
more than one of them, viz.:—(1) the inhalation of solid inorganic
particles, which are engulfed by the cells; (2) the presence in the
cells of coloured substances, solid or liquid, produced by the vital
activities of the sponge; and (3) the presence in the cells of peculiar
organized living bodies known as "green corpuscles."

Sponges living in muddy water are often nearly black. This is because
the cells of their parenchyma are gorged with very minute solid
particles of silt. If a sponge of the kind is kept in clean water for a
few days, it often becomes almost white. An interesting experiment is
easily performed to illustrate the absorption and final elimination of
solid colouring matter by placing a living sponge (small specimens of
Spongilla carteri are suitable) in a glass of clean water, and
sprinkling finely powdered carmine in the water. In a few hours the
sponge will be of a bright pink colour, but if only a little carmine is
used at first and no more added, it will regain its normal greyish hue
in a few days.

The colouring matter produced by the sponge itself is of two
kinds—pigment, which is probably a waste product, and the
substances produced directly by the ingestion of food or in the process
of its digestion. When pigment is produced it takes the form of minute
granules lying in the cells of the parenchyma, the dermal membrane being
as a rule colourless. Very little is known about the pigments of
freshwater sponges, and even less about the direct products of
metabolism. It is apparently the latter, however, that give many
otherwise colourless sponges a slight pinkish or yellowish tinge
directly due to the presence in cells of the parenchyma of minute liquid
globules. In one form of Spongilla carteri these globules turn of
a dark brown colour if treated with alcohol. The brilliant colour of
Pectispongilla aurea is due not to solid granules but to a liquid
or semi-liquid substance contained in the cells.

The green corpuscles of the Spongillidæ are not present in all
species. There is every reason to think that they represent a stage in
the life-history of an alga, and that they enter the sponge in an active
condition (see p. 49).

A fourth cause for the coloration of freshwater sponges may be noted
briefly. It is not a normal one, but occurs commonly in certain forms
(e. g., Spongilla alba var. bengalensis). This cause
is the growth in the canals and substance of the sponge of
parasitic[Pg
37] algaæ, which turn the whole organism of a dull green
colour. They do not do so, however, until they have reduced it to a
dying state. The commonest parasite of the kind is a filamentous species
particularly common in brackish water in the Ganges delta.

External Form and
Consistency.

Fig. 5.—Part of a type-specimen of Spongilla
lacustris subsp. reticulata (nat. size).

The external form of sponges is very variable, but each species,
subspecies, or variety of the Spongillidæ has normally a characteristic
appearance. The European race of Spongilla lacustris, for
example, consists in favourable circumstances of a flattened basal part
from which long cylindrical branches grow out; while in the Indian race
of the species these branches are flattened instead of being
cylindrical, and anastomose freely. The structure of the branches is
identical with that of the basal part. Many other species (for instance,
Spongilla bombayensis and S. ultima) never produce
branches but always consist of lichenoid[Pg 38] or cushion-shaped masses.
The appearance of Spongilla crateriformis, when it is growing on
a flattened surface which allows it to develop its natural form, is very
characteristic, for it consists of little flattened masses that seem to
be running out towards one another, just as though the sponge had been
dropped, spoonful by spoonful, in a viscous condition from a teaspoon.
Some species, such as Trochospongilla phillottiana, cover large
areas with a thin film of uniform thickness, while others (e. g.,
Spongilla alba and Ephydatia meyeni) consist of irregular
masses, the surface of which bears numerous irregular ridges or conical,
subquadrate, or digitate processes. In a few forms (e. g.,
Corvospongilla burmanica) the surface is covered with small
turret-like projections of considerable regularity, and some
(e. g., Spongilla crassissima) naturally assume a spherical
or oval shape with an absolutely smooth surface.

The production of long branches is apparently rare in tropical
freshwater sponges.

The form of the oscula is characteristic in many cases. No other
Indian species has them so large, or with such well-defined margins as
Spongilla carteri (Pl. II, fig. 1). In many species (Pl. II, fig.
3) they have a stellate appearance owing to the fact that grooves in the
substance of the sponge radiate round them beneath the external
membrane. In other species they are quite inconspicuous and very small.

Fig. 6.—Radial section through part of a dried
sponge of Spongilla crassissima (from Calcutta), × 5.

Spongillidæ differ greatly in consistency. Spongilla
crassissima and Corvospongilla lapidosa are almost stony,
although the former is extremely light, more like pumice than true
stone. Other species (e. g., Trochospongilla latouchiana)
are hard but brittle, while others again are soft and easily compressed,
as Spongilla lacustris, the variety mollis of S.
carteri, and S. crateriformis. The consistency of a sponge
depends on two factors—the number of spicules present, and the
amount of spongin. In Corvospongilla lapidosa the number of
spicules is very large indeed. They are not arranged so as to form a
reticulate skeleton but interlock in[Pg 39] all directions, and there
is hardly any spongin associated with them. In Spongilla
crassissima, on the other hand, the number of spicules although
large is not unusually so; but they form a very definitely reticulate
skeleton, and are bound together by an unusually profuse secretion of
spongin. In S. carteri var. mollis both spicules and
spongin are reduced to a minimum, and the parenchyma is relatively more
bulky than usual.

Variation.

Sponges are very variable organisms, and even a slight change in the
environment of the freshwater species often produces a considerable
change in form and structure. Some species vary in accordance with the
season, and others without apparent cause. Not only have many given rise
to subspecies and "varieties" that possess a certain stability, but most
if not all are liable to smaller changes that apparently affect both the
individual and the breed, at any rate for a period.

(a) Seasonal Variation.

Weltner has shown in a recent paper (Arch. Natg. Berlin, lxxiii (i),
p. 276, 1907) that in Europe those individuals of Ephydatia which
are found (exceptionally) in an active condition in winter differ
considerably both as regards the number of their cells and their anatomy
from those found in summer. In Calcutta the majority of the individuals
of Spongilla carteri that are found in summer have their external
surface unusually smooth and rounded, and contain in their parenchyma
numerous cells the protoplasm of which is gorged with liquid. These
cells give the whole sponge a faint pinkish tinge during life; but if it
is plunged in spirit, both the liquid in the cells and the spirit turn
rapidly of a dark brown colour. Specimens of Spongilla
crateriformis taken in a certain tank in Calcutta during the cold
weather had the majority of the skeleton-spicules blunt, while the
extremities of the gemmule-spicules were distinctly differentiated.
Specimens of the same species taken from the same tank in July had the
skeleton-spicules pointed, while the extremities of the gemmule-spicules
were much less clearly differentiated. I have been unable to confirm
this by observations made on sponges from other tanks, but it would
certainly suggest that at any rate the breed of sponges in the tank
first investigated was liable to seasonal variation.

(b) Variation due directly to Environment.

The characteristic external form of freshwater sponges is liable in
most cases to be altered as a direct result of changes in the[Pg 40]
environment. The following are two characteristic instances of this
phenomenon.

Certain shrubs with slender stems grow in the water at the edge of
Igatpuri Lake. The stems of these shrubs support many large examples of
Spongilla carteri, which are kept in almost constant motion owing
to the action of the wind on those parts of the shrubs that are not
under water. The surface of the sponges is so affected by the currents
of water thus set up against it that it is covered with deep grooves and
high irregular ridges like cockscombs. Less than a hundred yards from
the lake there is a small pond in which Spongilla carteri is also
abundant. Here it grows on stones at the bottom and has the
characteristic and almost smooth form of the species.

My second instance also refers in part to Igatpuri Lake.
Corvospongilla lapidosa is common in the lake on the lower
surface of stones, and also occurs at Nasik, about thirty miles away, on
the walls of a conduit of dirty water. In the latter situation it has
the form of large sheets of a blackish colour, with the surface
corrugated and the oscula inconspicuous, while in the clear waters of
the lake it is of a pale yellowish colour, occurs in small lichenoid
patches, and has its oscula rendered conspicuous, in spite of their
minute size, by being raised on little conical eminences in such a way
that they resemble the craters of volcanoes in miniature.

Both the European and the Indian races of Spongilla lacustris
fail to develop branches if growing in unfavourable conditions. In
specimens obtained from the River Spree near Berlin these structures are
sometimes many inches in length; while in mature specimens taken under
stones in Loch Baa in the Island of Mull the whole organism consisted of
a minute cushion-shaped mass less than an inch in diameter, and was also
deficient in spicules. Both these breeds belong to the same species, and
probably differ as a direct result of differences in environment.

(c) Variation without apparent cause.

Plate I in this volume illustrates an
excellent example of variation in external form to which it is
impossible to assign a cause with any degree of confidence. The three
specimens figured were all taken in the same pond, and at the same
season, but in different years. It is possible that the change in form,
which was not peculiar to a few individuals but to all those in several
adjacent ponds, was due to a difference in the salinity of the water
brought about by a more or less abundant rainfall; but of this I have
been able to obtain no evidence in succeeding years.

Many Spongillidæ vary without apparent cause as regards the shape,
size, and proportions of their spicules. This is the case as regards
most species of Euspongilla and Ephydatia, and is a fact
to which careful consideration has to be given in separating the
species.

Nutrition.[Pg 41]

Very little is known about the natural food of freshwater sponges,
except that it must be of an organic nature and must be either in a very
finely divided or in a liquid condition. The cells of the sponge seem to
have the power of selecting suitable food from the water that flows past
them, and it is known that they will absorb milk. The fact that they
engulf minute particles of silt does not prove that they lack the power
of selection, for extraneous matter is taken up by them not only as food
but in order that it may be eliminated. Silt would soon block up the
canals and so put a stop to the vital activity of the sponge, if it were
not got rid of, and presumably it is only taken into the cells in order
that they may pass it on and finally disgorge it in such a way or in
such a position that it may be carried out of the oscula. The siliceous
part of it may be used in forming spicules.

It is generally believed that the green corpuscles play an important
part in the nutrition of those sponges in which they occur, and there
can be no doubt that these bodies have the power peculiar to all
organisms that produce chlorophyll of obtaining nutritive substances
direct from water and carbonic oxide through the action of sunlight.
Possibly they hand on some of the nourishment thus obtained to the
sponges in which they live, or benefit them by the free oxygen given out
in the process, but many Spongillidæ do well without them, even when
living in identical conditions with species in which they abound.

Reproduction.

Both eggs and buds are produced by freshwater sponges (the latter
rarely except by one species), while their gemmules attain an
elaboration of structure not observed in any other family of
sponges.

Probably all Spongillidæ are potentially monœcious, that is to
say, able to produce both eggs and spermatozoa. In one Indian species,
however, in which budding is unusually common (viz. Spongilla
proliferens), sexual reproduction takes place very seldom, if ever.
It is not known whether the eggs of sponges are fertilized by
spermatozoa from the individual that produces the egg or by those of
other individuals, but not improbably both methods of fertilization
occur.

The egg of a freshwater sponge does not differ materially from that
of other animals. When mature it is a relatively large spherical cell
containing abundant food-material and situated in some natural cavity of
the sponge. In the earlier stages of its growth, however, it exhibits
amœboid movements, and makes its way through the common jelly. As
it approaches maturity it is surrounded by other cells which contain
granules of food-material. The food-material is apparently transferred
by them[Pg
42] in a slightly altered form to the egg. The egg has no
shell, but in some species (e. g. Ephydatia blembingia^[N]) it is surrounded, after
fertilization, by gland-cells belonging to the parent sponge, which
secrete round it a membrane of spongin. Development goes on within the
chamber thus formed until the larva is ready to assume a free life.

The spermatozoon is also like that of other animals, consisting of a
rounded head and a lash-like tail, the movements of which enable it to
move rapidly through the water. Spermatozoa are produced in
Spongilla from spherical cells not unlike the eggs in general
appearance. The contents of these cells divide and subdivide in such a
way that they finally consist of a mass of spermatozoa surrounded by a
single covering cell, which they finally rupture, and so escape.

Fig. 7.—Diagram of a vertical section through
the gemmule of Spongilla proliferens.

A=cellular contents; B=internal chitinous layer;
C=external chitinous layer; D=pneumatic coat; E=gemmule-spicule;
F=external membrane; G=foraminal tubule.

Gemmules are asexual reproductive bodies peculiar to the sponges, but
not to the Spongillidæ. They resemble the statoblasts of the
phylactolæmatous polyzoa in general structure as well as in function,
which is mainly that of preserving the race from destruction by such
agencies as drought, starvation, and temperatures that are either too
high or too low for its activities. This function they are enabled to
perform by the facts that they are provided with coverings not only very
hard but also fitted to resist the unfavourable agencies to which the
gemmules are likely[Pg 43] to be exposed, and that they contain
abundant food-material of which use can be made as soon as favourable
conditions occur again.

Internally the gemmule consists of a mass of cells containing
food-material in what may be called a tabloid form, for it consists of
minutely granular plate-like bodies. These cells are enclosed in a
flask-like receptacle, the walls of which consist of two chitinous
layers, a delicate inner membrane and an outer one of considerable
stoutness. The mouth of the flask is closed by an extension of the inner
membrane, and in some species is surrounded by a tubular extension of
the external membrane known as the foraminal tubule. Externally the
gemmule is usually covered by what is called a "pneumatic coat," also of
"chitin" (spongin), but usually of great relative thickness and
honeycombed by spaces which contain air, rendering the structure
buoyant. The pneumatic coat also contains the microscleres
characteristic of the species; it is often limited externally by a third
chitinous membrane, on which more gemmule-spicules sometimes lie
parallel to the surface.

The cells from which those of the gemmules are derived are akin in
origin to those that give rise to eggs and spermatozoa. Some zoologists
are therefore of the opinion that the development of the gemmule is an
instance of parthenogenesis—that is to say of an organism arising
from an egg that has not been fertilized. But some of the collar-cells,
although most of them originate from the external ciliated cells of the
larva, have a similar origin. The building-up of the gemmule affords an
excellent instance of the active co-operation that exists between the
cells of sponges, and of their mobility, for the food-material that has
to be stored up is brought by cells from all parts of the sponge, and
these cells retire after discharging their load into those of the young
gemmule.

The formation of the gemmule of Ephydatia blembingia, a
Malayan species not yet found in India, is described in detail by Dr. R.
Evans (Q. J. Microsc. Sci. London, xliv, p. 81, 1901).

Gemmules are produced by the freshwater sponges of Europe, N. America
and Japan at the approach of winter, but in the tropical parts of India
they are formed more frequently at the approach of the hot weather (p.
4). After they are fully formed the sponge that has produced them dies,
and as a rule disintegrates more or less completely. In some species,
however, the greater part of the skeleton remains intact, if it is not
disturbed, and retains some of the gemmules in its meshwork, where they
finally germinate. Other gemmules are set free. Some of them float on
the surface of the water; others sink to the bottom. In any case all of
them undergo a period of quiescence before germinating. It has been
found that they can be kept dry for two years without dying.

The function of the special spicules with which the gemmules[Pg 44] of the
Spongillidæ are provided appears to be not only to protect them but more
especially to weight them to the extent suitable to the habits of each
species. Species that inhabit running water, for example, in some cases
have heavier gemmule-spicules than those that live in stagnant water,
and their gemmules are the less easily carried away by the currents of
the river. The gemmules of sponges growing in lakes are sometimes
deficient in spicules. This is the case as regards the form of
Spongilla lacustris found in Lake Baa, Isle of Mull, as regards
S. helvetica from the Lake of Geneva, S. moorei from Lake
Tanganyika, and S. coggini from Tali-Fu in Yunnan; also as
regards the species of Spongilla and Ephydatia found in
Lake Baikal, many of the sponges of which are said never to produce
gemmules.

Except in the genus Corvospongilla and the subgenus
Stratospongilla, in both of which the air-spaces of the gemmules
are usually no more than cavities between different chitinous membranes,
the pneumatic coat is either "granular" or "cellular." Neither of these
terms, however, must be understood in a physiological sense, for what
appear to be granules in a granular coat are actually minute bubbles of
air contained in little cavities in a foam-like mass of chitin (or
rather spongin), while the cells in a cellular one are only larger and
more regular air-spaces with thin polygonal walls and flat horizontal
partitions. The walls of these spaces are said in some cases to contain
a considerable amount of silica.

The gemmules with their various coverings are usually spherical in
shape, but in some species they are oval or depressed in outline. They
lie as a rule free in the substance of the sponge, but in some species
adhere at its base to the object to which it is attached. In some
species they are joined together in groups, but in most they are quite
free one from another.

Reproductive buds^[O] are produced, so
far as is known, by very few Spongillidæ, although they are common
enough in some other groups of sponges. In the only freshwater species
in which they have been found to form a habitual means of reproduction,
namely in Spongilla proliferens, they have much the appearance of
abortive branches, and it is possible that they have been overlooked for
this reason in other species, for they were noticed by Laurent in
Spongilla lacustris as long ago as 1840 (CR. Sé. Acad. Sci.
Paris, xi, p. 478). The buds noticed by Laurent, however, were only
produced by very young sponges, and were of a different nature from
those of S. proliferens, perhaps representing a form of fission
rather than true budding (see 'Voyage de la Bonite: Zoophytologie,'
Spongiaires, pl. i (Paris, 1844)).

In Spongilla proliferens, a common Indian species, the buds
arise[Pg
45] as thickenings of the strands of cells accompanying the
radiating spicule-fibres of the skeleton, which project outwards from
the surface of the sponge. The thickenings originate beneath the surface
and contain, at the earliest stage at which I have as yet examined them,
all the elements of the adult organism (i. e. flesh-spicules,
ciliated chambers, efferent and afferent canals, parenchyma-cells of
various sorts) except skeleton fibres, gemmules, and a dermal membrane.
A section at this period closely resembles one of an adult sponge,
except that the structure is more compact, the parenchyma being
relatively bulky and the canals of small diameter.

Laurent observed reproduction by splitting in young individuals of
Spongilla, but I have not been able to obtain evidence myself
that this method of reproduction occurs normally in Indian species. In
injured specimens of Spongilla carteri, however, I have observed
a phenomenon that seems to be rather an abnormal form of budding, little
rounded masses of cells making their way to the ends of the radiating
skeleton fibres and becoming transformed into young sponges, which break
loose and so start an independent existence. Possibly the buds observed
by Laurent in S. lacustris were of a similar nature.

Development.

(a) From the Egg.

After fertilization, the egg, lying in its cavity in the sponge,
undergoes a complete segmentation; that is to say, becomes divided into
a number of cells without any residuum remaining. The segmentation,
however, is not equal, for it results in the formation of cells of two
distinct types, one larger and less numerous than the other. As the
process continues a pear-shaped body is produced, solid at the broader
end, which consists of the larger cells, but hollow at the other.
Further changes result in the whole of the external surface becoming
ciliated or covered with fine protoplasmic lashes, each of which arises
from a single small cell; considerable differentiation now takes place
among the cells, and spicules begin to appear. At this stage or earlier
(for there seem to be differences in different species and individuals
as to the stage at which the young sponge escapes) the larva makes its
way out of the parent sponge. After a brief period of free life, in
which it swims rapidly through the water by means of its cilia, it fixes
itself by the broad end to some solid object (from which it can never
move again) and undergoes a final metamorphosis. During this process the
ciliated cells of the external layer make their way, either by a
folding-in of the whole layer or in groups of cells, into the interior,
there change into collar-cells and arrange themselves in special
cavities—the ciliated chambers of the adult. Finally an osculum,
pores, &c., are formed, and the sponge is complete.

[Pg
46]This, of course, is the merest outline of what occurs;
other changes that take place during the metamorphosis are of great
theoretical interest, but cannot be discussed here. The student may
refer to Dr. R. Evans's account of the larval development of
Spongilla lacustris in the Q. J. Microsc. Sci. London, xlii, p.
363 (1899).

(b) From the Gemmule.

The period for which the gemmule lies dormant probably depends to
some extent upon environment and to some extent on the species to which
it belongs. Carter found that if he cleaned gemmules with a handkerchief
and placed them in water exposed to sunlight, they germinated in a few
days; but in Calcutta gemmules of Spongilla alba var.
bengalensis treated in this way and placed in my aquarium at the
beginning of the hot weather, did not germinate until well on in the
"rains." Even then, after about five months, only a few of them did so.
Zykoff found that in Europe gemmules kept for two years were still alive
and able to germinate.

Germination consists in the cellular contents of the gemmule bursting
the membrane or membranes in which they are enclosed, and making their
way out of the gemmule in the form of a delicate whitish mass, which
sometimes issues through the natural aperture in the outer chitinous
coat and sometimes through an actual rent in this coat. In the latter
case the development of the young sponge is more advanced than in the
former.

The fullest account of development from the gemmule as yet published
is by Zykoff, and refers to Ephydatia in Europe (Biol. Centralbl.
Berlin, xii, p. 713, 1892).

His investigations show that the bursting of the gemmule is not
merely a mechanical effect of moisture or any such agency but is due to
development of the cellular contents, which at the time they escape have
at least undergone differentiation into two layers. Of the more
important soft structures in the sponge the osculum is the first to
appear, the ciliated chambers being formed later. This is the opposite
of what occurs in the case of the bud, but in both cases the aperture
appears to be produced by the pressure of water in the organism. The
manner and order in which the different kinds of cells originate in the
sponge derived from a gemmule give support to the view that the
primitive cell-layers on which morphologists lay great stress are not of
any great importance so far as sponges are concerned.

(c) Development of the Bud.

As the bud of Spongilla proliferens grows it makes its way up
the skeleton-fibre to which it was originally attached, pushing the
dermal membrane, which expands with its growth, before it. The[Pg 47]
skeleton-fibre does not, however, continue to grow in the bud, in which
a number of finer fibres make their appearance, radiating from a point
approximately at the centre of the mass. As the bud projects more and
more from the surface of the sponge the dermal membrane contracts at its
base, so as finally to separate it from its parent. Further details are
given on p. 74.

Habitat.

Mr. Edward Potts^[P], writing on the
freshwater sponges of North America, says:—"These organisms have
occasionally been discovered growing in water unfit for domestic uses;
but as a rule they prefer pure water, and in my experience the finest
specimens have always been found where they are subjected to the most
rapid currents." True as this is of the Spongillidæ of temperate
climates, it is hardly applicable to those of tropical India, for in
this country we find many species growing most luxuriantly and commonly
in water that would certainly be considered unfit for domestic purposes
in a country in which sanitation was treated as a science. Some species,
indeed, are only found in ponds of water polluted by human agency, and
such ponds, provided that other conditions are favourable, are perhaps
the best collecting grounds. Other favourable conditions consist in a
due mixture of light and shade, a lack of disturbance such as that
caused by cleaning out the pond, and above all in the presence of
objects suitable for the support of sponges.

I do not know exactly why light and shade must be mixed in a habitat
favourable for the growth of sponges, for most species prefer shade, if
it be not too dense; but it is certainly the case that, with a few
exceptions, Indian Spongillidæ flourish best in water shaded at the
edges by trees and exposed to sunlight elsewhere. One of the exceptions
to this rule is the Indian race of Spongilla lucustris, which is
found in small pools of water in sand-dunes without a particle of shade.
Several species are only found on the lower surface of stones and roots
in circumstances which do not suggest that their position merely
protects them from mud, which, as Mr. Potts points out, is their "great
enemy." A notable instance is Trochospongilla pennsylvanica,
which is found hiding away from light in America and Europe as well as
in India.

It is curious that it should be easy to exterminate the sponges in a
pond by cleaning it out, for one would have thought that sufficient
gemmules would have remained at the edge, or would have been brought
rapidly from elsewhere, to restock the water. Mr. Green has, however,
noted that Spongilla carteri has disappeared for some years from
a small lake at Peradeniya in which it was formerly abundant, owing to
the lake having been cleaned[Pg 48] out, and I have made similar
observations on several occasions in Calcutta.

The question of the objects to which sponges attach themselves is one
intimately connected with that of the injury done them by mud. The delta
of the Ganges is one of the muddiest districts on earth. There are no
stones or rocks in the rivers and ponds, but mud everywhere. If a sponge
settles in the mud its canals are rapidly choked, its vital processes
cease, and it dies. In this part of India, therefore, most sponges are
found fixed either to floating objects such as logs of wood, to vertical
objects such as the stems of bulrushes and other aquatic plants, or to
the tips of branches that overhang the water and become submerged during
the "rains." In Calcutta man has unwittingly come to the assistance of
the sponges, not only by digging tanks but also by building
"bathing-ghats" of brick at the edge, and constructing, with æsthetic
intentions if not results, masses of artificial concrete rocks in or
surrounding the water. There are at least two sponges (the typical form
of Spongilla alba and Ephydatia meyeni) which in Calcutta
are only found attached to such objects. The form of S. alba,
however, that is found in ponds of brackish water in the Gangetic delta
has not derived this artificial assistance from man, except in the few
places where brick bridges have been built, and attaches itself to the
stem and roots of a kind of grass that grows at the edge of brackish
water. This sponge seems to have become immune even to mud, the
particles of which are swallowed by its cells and finally got rid of
without blocking up the canals.

Several Indian sponges are only found adhering to stones and rocks.
Among these species Corvospongilla lapidosa and our
representatives of the subgenus Stratospongilla are noteworthy.
Some forms (e. g. Spongilla carteri and S.
crateriformis) seem, however, to be just as much at home in muddy as
in rocky localities, although they avoid the mud itself.

There is much indirect evidence that the larvæ of freshwater sponges
exercise a power of selection as regards the objects to which they affix
themselves on settling down for life.

Few Spongillidæ are found in salt or brackish water, but Spongilla
alba var. bengalensis has been found in both, and is abundant
in the latter; indeed, it has not been found in pure fresh water.
Spongilla travancorica has only been found in slightly brackish
water, while S. lacustris subsp. reticulata and Dosilia
plumosa occur in both fresh and brackish water, although rarely in
the latter. The Spongillidæ are essentially a freshwater family, and
those forms that are found in any but pure fresh water must be regarded
as aberrant or unusually tolerant in their habits, not as primitive
marine forms that still linger halfway to the sea.

[Pg 49]Animals and Plants
commonly associated with Freshwater Sponges.

(a) Enemies.

Freshwater sponges have few living enemies. Indeed, it is difficult
to say exactly what is an enemy of a creature so loosely organized as a
sponge. There can be little doubt, in any case, that the neuropteroid
larva (Sisyra indica) which sucks the cells of several species
should be classed in this category, and it is noteworthy that several
species of the same genus also occur in Europe and N. America which also
attack sponges. Other animals that may be enemies are a midge larva
(Tanypus sp.) and certain worms that bore through the parenchyma
(p. 93), but I know of no animal that devours sponges bodily, so long as
they are uninjured. If their external membrane is destroyed, they are
immediately attacked by various little fish and also by snails of the
genera Limnæa and Planorbis, and prawns of the genus
Palæmon.

Their most active and obvious enemy is a plant, not an
animal,—to wit, a filamentous alga that blocks up their canals by
its rapid growth (p. 79).

(b) Beneficial Organisms.

The most abundant and possibly the most important organisms that may
be considered as benefactors to the Spongillidæ are the green corpuscles
that live in the cells of certain species (fig. 2, p. 31), notably
Spongilla lacustris, S. proliferens, and Dosilia
plumosa. I have already said that these bodies are in all
probability algæ which live free in the water and move actively at one
stage of their existence, but some of them are handed on directly from a
sponge to its descendants in the cells of the gemmule. In their
quiescent stage they have been studied by several zoologists, notably by
Sir Ray Lankester^[Q] and Dr. W.
Weltner^[R], but the strongest light that has
been cast on their origin is given by the researches of Dr. F. W. Gamble
and Mr. F. Keeble (Q. J. Microsc. Sci. London, xlvii, p. 363, 1904, and
li, p. 167, 1907). These researches do not refer directly to the
Spongillidæ but to a little flat-worm that lives in the sea,
Convoluta roscoffiensis. The green corpuscles of this worm so
closely resemble those of Spongilla that we are justified in
supposing a similarity of origin. It has been shown by the authors cited
that the green corpuscles of the worm are at one stage minute
free-living organisms provided at one end with four flagella and at the
other with a red pigment spot. The investigators are of the opinion that
these organisms exhibit[Pg 50] the essential characters of the algæ
known as Chlamydomonadæ, and that after they have entered the worm they
play for it the part of an excretory system.

As they exist in the cells of Spongilla the corpuscles are
minute oval bodies of a bright green colour and each containing a highly
refractile colourless granule. A considerable number may be present in a
single cell. It is found in European sponges that they lose their green
colour if the sponge is not exposed to bright sunlight. In India,
however, where the light is stronger, this is not always the case. Even
when the colour goes, the corpuscles can still be distinguished as pale
images of their green embodiment. They are called Chlorella by
botanists, who have studied their life-history but have not yet
discovered the full cycle. See Beyerinck in the Botan. Zeitung for 1890
(vol. xlviii, p. 730, pl. vii; Leipzig), and for further references
West's 'British Freshwater Algæ,' p. 230 (1904).

The list of beneficent organisms less commonly present than the green
corpuscles includes a Chironomus larva that builds parchment-like
tubes in the substance of Spongilla carteri and so assists in
supporting the sponge, and of a peculiar little worm (Chætogaster
spongillæ^[S]) that appears to
assist in cleaning up the skeleton of the same sponge at the approach of
the hot weather and in setting free the gemmules (p. 93).

(c) Organisms that take shelter in the Sponge or
adhere to it externally.

There are many animals which take shelter in the cavities of the
sponge without apparently assisting it in any way. Among these are the
little fish Gobius alcockii, which lays its eggs inside the
oscula of S. carteri, thus ensuring not only protection but also
a proper supply of oxygen for them (p. 94); the molluscs
(Corbula, spp.) found inside S. alba var.
bengalensis (p. 78); and the Isopod (Tachæa spongillicola)
that makes its way into the oscula of Spongilla carteri and S.
crateriformis (pp. 86, 94).

In Europe a peculiar ciliated Protozoon (Trichodina spongillæ)
is found attached to the external surface of freshwater sponges. I have
noticed a similar species at Igatpuri on Spongilla crateriformis,
but it has not yet been identified. It probably has no effect, good or
bad, on the sponge.

Freshwater Sponges in relation
to Man.

In dealing with Spongilla carteri I have suggested that
sponges may be of some hygienic importance in absorbing putrid organic
matter from water used both for ablutionary and for drinking purposes,
as is so commonly the case with regard to ponds in India. Their bad
odour has caused some species of Spongillidæ[Pg 51] to be regarded as capable
of polluting water, but a mere bad odour does not necessarily imply that
they are insanitary.

Unless my suggestion that sponges purify water used for drinking
purposes by absorbing putrid matter should prove to be supported by
fact, the Spongillidæ cannot be said to be of any practical benefit to
man. The only harm that has been imputed to them is that of polluting
water^[T], of blocking up water-pipes by their
growth—a very rare occurrence,—and of causing irritation to
the human skin by means of their spicules—a still rarer one. At
least one instance is, however, reported in which men digging in a place
where a pond had once been were attacked by a troublesome rash probably
due to the presence of sponge-spicules in the earth, and students of the
freshwater sponges should be careful not to rub their eyes after
handling dried specimens.

Indian Spongillidæ Compared
With Those of Other Countries.

In Weltner's catalogue of the freshwater sponges (1895) seventy-six
recent species of Spongillidæ (excluding Lubosmirskia) are
enumerated, and the number now known is well over a hundred. In India we
have twenty-nine species, subspecies, and varieties, while from the
whole of Europe only about a dozen are known. In the neighbourhood of
Calcutta nine species, representing three genera and a subgenus, have
been found; all of them occur in the Museum tank. The only other region
of similar extent that can compare with India as regards the richness of
its freshwater sponge fauna is that of the Amazon, from which about
twenty species are known. From the whole of North America, which has
probably been better explored than any other continent so far as
Spongillidæ are concerned, only twenty-seven or twenty-eight species
have been recorded.

The Indian species fall into seven genera, one of which
(Spongilla) consists of three subgenera. With one exception (that
of Pectispongilla, which has only been found in Southern India)
these genera have a wide distribution over the earth's surface, and this
is also the case as regards the subgenera of Spongilla. Four genera
(Heteromeyenia, Acalle, Parmula, and
Uruguaya) that have not yet been found in India are known to
exist elsewhere.

Five of the Indian species are known to occur in Europe, viz.,
Spongilla lacustris, S. crateriformis, S. carteri,
S. fragilis, Trochospongilla pennsylvanica; while
Ephydatia meyeni is intermediate between the two commonest
representatives of its genus in the Holarctic Zone, Ephydatia
fluviatilis and E. mülleri. Of the species that occur both in
India and in Europe, two (Spongilla[Pg 52] lacustris and
S. fragilis) are found in this country in forms sufficiently
distinct to be regarded as subspecies or local races. Perhaps this
course should also be taken as regards the Indian forms of S.
carteri, of which, however, the commonest of the Indian races would
be the typical one; but S. crateriformis and T.
pennsylvanica seem to preserve their specific characters free from
modification, whether they are found in Europe, Asia, or America.

The freshwater sponges of Africa have been comparatively little
studied, but two Indian species have been discovered, S.
bombayensis in Natal and S. alba var. cerebellata in
Egypt. Several of the species from the Malabar Zone are, moreover,
closely allied to African forms (p. 11).

Fossil Spongillidæ.

The Spongillidæ are an ancient family. Young described a species
(Spongilla purbeckensis) from the Upper Jurassic of Dorset (Geol.
Mag. London (new series) v, p. 220 (1878)), while spicules, assigned by
Ehrenberg to various genera but actually those of Spongilla
lacustris or allied forms, have been found in the Miocene of Bohemia
(see Ehrenberg's 'Atlas für Micro-Geologie,' pl. xi (Leipzig, 1854), and
Traxler in Földt. Közl., Budapest, 1895, p. 211). Ephydatia is
also known in a fossil condition, but is probably less ancient than
Spongilla.

Ehrenberg found many sponge spicules in earth from various parts of
the Indian Empire (including Baluchistan, Mangalore, Calcutta, the
Nicobars and Nepal) and elsewhere, and it might be possible to guess at
the identity of some of the more conspicuous species figured in his
'Atlas.' The identification of sponges from isolated spicules is,
however, always a matter of doubt, and in some cases Ehrenberg probably
assigned spicules belonging to entirely different families or even
orders to the same genus, while he frequently attributed the different
spicules of the same species to different genera. Among his fossil (or
supposed fossil) genera that may be assigned to the Spongillidæ wholly
or in part are Aphidiscus, Spongolithis,
Lithastericus and Lithosphæridium, many of the species of
these "genera" certainly belonging to Spongilla and
Ephydatia.

Oriental Spongillidæ not yet
found in India.

Few freshwater sponges that have not been found in India are as yet
known from the Oriental Region, and there is positive as well as
negative evidence that Spongillidæ are less abundant in Malaysia than in
this country. The following list includes the names of those that have
been found, with notes regarding each species. It is quite possible that
any one of them may be found at any time within the geographical
boundaries laid down for this 'Fauna.' I have examined types or co-types
in all cases except that of Ephydatia fortis, Weltner.

[Pg
53]I. Spongilla (Euspongilla)
microsclerifera*, Annandale (Philippines). P. U.S. Mus. xxxvii,
p. 131 (1909).

This sponge is closely related to S.
lacustris, but apparently does not produce branches. It is
remarkable for the enormous number of microscleres in its
parenchyma.

II. S. (Euspongilla) philippinensis*, Annandale
(Philippines). P. U.S. Mus. xxxvi, p. 629 (1909).

Related to S. alba and still more closely
to S. sceptrioides of Australia. From the former it is readily
distinguished by having minutely spined megascleres, green corpuscles,
slender gemmule-spicules with short spines and no free microscleres.

III. S. (? Euspongilla) yunnanensis*, Annandale
(W. China). Rec. Ind. Mus. v, p. 197 (1910).

Apparently allied to S. philippinensis
but with smooth skeleton-spicules and a more delicate skeleton.

IV. S. (Stratospongilla) sinensis*, Annandale
(Foochow, China). P. U.S. Mus. xxxviii, p. 183 (1910).

This species and S. clementis are
referred to Stratospongilla with some doubt. Their gemmules are
intermediate in structure between those of that subgenus and those of
Euspongilla. In S. sinensis the gemmules are packed
together in groups at the base of the sponge, and their spicules are
smooth, stout, and gradually pointed.

V. S. (Stratospongilla) clementis*, Annandale
(Philippines). P. U.S. Mus. xxxvi, p. 631 (1909).

The gemmules are single and closely adherent at
the base of the sponge. Their spicules are very slender and minutely
spined.

VI. S. (? Stratospongilla) coggini*, Annandale
(W. China). Rec. Ind. Mus. v, p. 198 (1910).

The gemmules apparently lack microscleres. They
resemble those of S. clementis, to which the species is probably
related, in other respects. The skeleton-spicules are spiny and rather
stout, the species being strongly developed at the two ends.

VII. S. (Stratospongilla) sumatrana*, Weber
(Malay Archipelago). Zool. Ergebnisse einer Reise in Niederländisch
Ost-Indien, i. p. 38 (1890).

Closely allied to S. indica (p. 100) but
with pointed skeleton-spicules.

VIII. Ephydatia fortis, Weltner (Philippines). Arch.
Naturgesch. lxi(i), p. 141 (1895).

This species is remarkable for the great
development of the spines on the shaft of the gemmule-spicules.

[Pg
54]IX. Ephydatia bogorensis*, Weber (Malay
Archipelago). Zool. Ergebnisse einer Reise in Niederländisch Ost-Indien,
i, p. 33 (1890).

The gemmule-spicules have rather narrow flattish
disks, the edge of which is feebly but closely serrated.

X. E. blembingia*, Evans (Malay Peninsula). Q. J. Microsc.
Sci. London, xliv, p. 81 (1901).

The gemmules resemble those of Dosilia
plumosa but are spherical. There are no free microscleres.

XI. Tubella vesparium*, v. Martens (Borneo). Arch. Naturg.
Berlin, xxxiv, p. 62 (1868).

Closely related to T. vesparioides (p.
189), but with spiny megascleres.

As regards Spongilla decipiens*, Weber, from the Malay
Archipelago, see p. 97.

II.

History of the Study of Freshwater
Sponges.

The bath-sponge was known to the Greeks at an early date, and Homer
refers to it as being used for cleansing furniture, for expunging
writing, and for ablutionary purposes. He also mentions its peculiar
structure, "with many holes." "Many things besides," wrote the English
naturalist Ray in his 'Historia Plantarum' (1686), "regarding the powers
and uses of sponges have the Ancients: to them refer." Ray himself
describes at least one freshwater species, which had been found in an
English river, and refers to what may be another as having been brought
from America. In the eighteenth century Linné, Pallas and other authors
described the commoner European Spongillidæ in general terms, sometimes
as plants and sometimes as animals, more usually as zoophytes or
"plant-animals" partaking of the nature of both kingdoms. The gemmules
were noted and referred to as seeds. The early naturalists of the
Linnæan Epoch, however, added little to the general knowledge of the
Spongillidæ, being occupied with theory in which theological disputes
were involved rather than actual observation, and, notwithstanding the
fact that the animal nature of sponges was clearly demonstrated by
Ellis^[U] in 1765, it was not until the
nineteenth century was well advanced that zoologists could regard
sponges in anything like an impartial manner.

One of the pioneers in the scientific study of the freshwater[Pg 55] forms
was the late Dr. H. J. Carter, who commenced his investigations, and
carried out a great part of them, in Bombay with little of the apparatus
now considered necessary, and with a microscope that must have been
grossly defective according to modern ideas. His long series of papers
(1848-1887) published in the 'Annals and Magazine of Natural History' is
an enduring monument to Indian zoology, and forms the best possible
introduction to the study of the Spongillidæ. Even his earlier mistakes
are instructive, for they are due not so much to actual errors in
observation as to a faithful transcription of what was observed with
faulty apparatus.

Contemporary with Carter were two authors whose monographs on the
freshwater sponges did much to advance the study of the group, namely,
J. S. Bowerbank, whose account of the species known at the time was
published in the 'Proceedings of the Zoological Society of London' in
1882, and the veteran American naturalist Mr. Edward Potts, whose study
of the freshwater sponges culminated in his monograph published in the
'Proceedings of the Academy of Natural Sciences of Philadelphia' in
1887. Carter's own revision of the group was published in the 'Annals
and Magazine of Natural History' in 1881. The names of Vejdovsky, who
prefaced Potts's monograph with an account of the European species, and
of Dybowsky, who published several important papers on classification,
should also be mentioned, while Weltner's catalogue of the known species
(1895) is of the greatest possible value to students of the group.

Many authors have dealt with the physiology, reproduction and
development of the Spongillidæ, especially in recent years; Dr. R.
Evans's description of the larva of Spongilla lacustris (1899),
and his account of the development of the gemmule in Ephydatia
blembingia (1901), Zykoff's account of the development of the
gemmule and of the sponge from the gemmule (1892), and Weltner's
observations on colour and other points (1893, 1907), may be mentioned
in particular. Laurent's observations on development (1844), which were
published in the 'Voyage de la Bonite,' and especially the exquisite
plates which accompany them, have not received the notice they deserve,
probably on account of their method of publication.

Literature.

The fullest account of the literature on the Spongillidæ as yet
published will be found in the first of Weltner's 'Spongillidenstudien'
(Archiv für Naturgeschichte, lix (i), p. 209, 1893). Unfortunately it
contains no references of later date than 1892. The following list is
not a complete bibliography, but merely a list of books and papers that
should prove of use to students of the Oriental Spongillidæ.

[Pg
56]

[K]
Except in "Proterospongia," an organism of doubtful affinities
but not a sponge. It consists of a mass of jelly containing ordinary
cells, with collar-cells outside.

[L]
Cf. Weltner, "Spongillidenstudien, V," Arch. Naturg. Berlin,
lxxiii (i), p. 273 (1907).

[M]
It is difficult to see any trace of them in thin microtome sections. A
fragment of the membrane must be mounted whole.

[N]
Rec. Ind. Mus. i, p. 269 (1907).

[O]
Proliferation whereby more than one osculum is produced is really a form
of budding, but in most sponges this has become no longer a mode of
reproduction but the normal method by which size is increased, and must
therefore be considered merely as a vegetative process.

[P]
P. Ac. Philad. 1887, p. 162.

[Q]
Q. J. Microsc. Sci. London, xxii. p. 229 (1882).

[R]
Arch. Naturg. Berlin, lix (i), p. 260 (1893).

[S]
Journ. As. Soc. Beng. n. s. ii, 1906, p. 189.

[T]
See Potts, Proc. Ac. Philad. 1884, p. 28.

[U]
Phil. Trans. Roy. Soc. lv, p. 280.

[V]
Descriptions of Siberian sponges are not included in these
references.

[Pg
61]

GLOSSARY OF TECHNICAL TERMS USED IN PART I.

[Pg
63]

SYSTEMATIC LIST OF THE INDIAN SPONGILLIDÆ.

[Types, schizotypes, or cotypes have been
examined in the case of all species, &c. , whose names are marked
thus, *.]

Genus 1. Spongilla, Lamarck (1816).

Subgenus A. Euspongilla,
Vejdovsky (1883).

1.

? S. lacustris, auct. (perhaps in N.W.
India).

1a.

S. lacustris subsp. reticulata*,
Annandale (1907).

2.

S. proliferens*, Annandale (1907).

3.

S. alba*, Carter (1849).

3a.

S. alba var. cerebellata, Bowerbank
(1863).

3b.

S. alba var. bengalensis*, Annandale
(1906).

4.

S. cinerea*, Carter (1849).

5.

S. travancorica*, Annandale (1909).

6.

S. hemephydatia*, Annandale (1909).

7.

S. crateriformis* (Potts) (1882).

Subgenus B. Eunapius, J.
E. Gray (1867).

8.

S. carteri*, Carter (1849).

8a.

S. carteri var. mollis*, nov.

8b.

S. carteri var. cava*, nov.

8c.

S. carteri var. lobosa*, nov.

9a.

S. fragilis subsp. calcuttana*,
nov.

9b.

S. fragilis var. decipiens, Weber

(probably Malaysian, not Indian).

10.

S. gemina*, sp. nov.

11.

S. crassissima*, Annandale (1907).

11a.

S. crassissima var. crassior*,
Annandale (1907).

Subgenus C. Stratospongilla, Annandale (1909).

12.

S. indica*, Annandale (1908).

13.

S. bombayensis*, Carter (1882).

14.

S. ultima*, Annandale (1910).

Genus 2. Pectispongilla, Annandale
(1909).

15.

P. aurea*, Annandale (1909).

15a.

P. aurea var. subspinosa*, nov.

[Pg
64]

Genus 3. Ephydatia, Lamouroux (1816).

16.

E. meyeni* (Carter) (1849).

Genus 4. Dosilia, J. E. Gray (1867).

17.

D. plumosa* (Carter) (1849).

Genus 5. Trochospongilla, Vejdovsky
(1883).

18.

T. latouchiana*, Annandale (1907).

19.

T. phillottiana*, Annandale (1907).

20.

T. pennsylvanica* (Potts) (1882).

Genus 6. Tubella, Carter (1881).

21.

T. vesparioides*, Annandale (1908).

Genus 7. Corvospongilla, nov.

22.

C. burmanica* (Kirkpatrick) (1908).

23.

C. lapidosa* (Annandale) (1908).

[Pg
65]

Order HALICHONDRINA.

Siliceous monaxon sponges in which the horny skeleton is
much reduced or absent and the spicular skeleton is more or less
definitely reticulate. The microscleres are usually rod-like and rarely
have more than one main axis.

Family SPONGILLIDÆ.

Spongilladæ, J. E. Gray, P.
Zool. Soc. London, 1867, p. 550.

Freshwater Halichondrina which at certain seasons produce
gemmules armed with peculiar microscleres. Two distinct kinds of
microsclere are often present, that associated with the gemmule
sometimes consisting of a vertical shaft at the ends of which transverse
disks or rotulæ are borne. There is always at least a trace of a
subdermal cavity.

Many authors divide the Spongillidæ into two
subfamilies:—Spongillinæ (or Euspongillinæ), in which the
gemmule-spicules have no transverse rotulæ, and Meyeninæ (or
Ephydatiinæ), in which they have rotules at one or both ends. So
gradual, however, is the transition that I find it difficult to decide
in one instance to which of two genera, typical respectively of the two
"subfamilies," a species should be assigned. Minchin in his account of
the Porifera in Lankester's "Treatise on Zoology" (1900) regards the
Spongillidæ merely as a subfamily of the Heterorrhaphidæ, and there
certainly are few differences of a definite nature between them and the
marine family (or subfamily) Remeridæ.

Key to the Indian Genera of Spongillidæ.

The most distinct genus of Spongillidæ not yet found in India is
Heteromeyenia, Potts. It is easily distinguished from all others
by the fact that the birotulate spicules of the gemmule are of two quite
distinct kinds, which occur together on every mature gemmule.
Heteromeyenia is represented by several American species, one of
which has been found in Europe. Acalle, J. E. Gray, which is
represented by a single South American species (Spongilla
recurvata, Bowerbank), is related to Heteromeyenia but has
one kind of gemmule-spicule tubelliform, the other birotulate. Probably
Uraguaya, Carter, should be regarded as a subgenus of
Trochospongilla with an unusually solid skeleton; it is peculiar
to S. America. Parmula, Carter (=Drulia, Gray) includes
South American forms allied to Tubella, but with the shaft of the
gemmule-spicule degenerate and consisting of a mere projection in the
centre of a shield-like body, which represents the lower rotule. The
status of Potamolepis, Marshall, originally described from the
Lake of Galilee, is very doubtful; possibly some or all of its species
belong to the subgenus of Spongilla here called
Stratospongilla (p. 100); but they are stated never to produce
gemmules. The same is the case as regards Pachydictyum, Weltner,
which consists of a single species from Celebes.

The sponges from Lake Baikal assigned by Weltner (Arch. Naturg. lxi
(i) p. 131) to the subfamily Lubomirskinæ are of doubtful position and
need not be considered here; while Lessepsia, Keller, from one of
the salt lakes on the Suez Canal, certainly does not belong to the
family, although it is assigned to it by von Lendenfeld (Mon. Horny
Sponges, p. 904 (1889)) and subsequently by Minchin (Porifera, p. 152,
in Lankester's Treatise on Zoology, part ii (1900)).

[Pg
67]

Genus 1. SPONGILLA, Lamarck (Carter
emend.).

Type, Spongilla lacustris,
auctorum.

Spongillidæ in which the gemmules have (normally) cylindrical or
subcylindrical spicules that are sharp or blunt at the ends, without a
distinct transverse disk or disks and without comb-like vertical rows of
spines.

The skeleton is variable in structure, sometimes being almost
amorphous, sometimes having well-defined radiating and transverse fibres
firmly compacted with spongin. The skeleton-spicules are either sharp or
blunt at the ends. Flesh-spicules are often absent; when present they
are needle-like and resemble the gemmule-spicules in general structure;
they have not even rudimentary rotules at their ends. The gemmules
either lie free in the substance of the sponge or are attached to its
support; sometimes they adhere together in free or attached groups.

Spongilla is undoubtedly the most primitive genus of the
Spongillidæ, its spicules showing less sign of specialization than those
of any other genus included in the family. As a fossil it goes back at
any rate to the Upper Jurassic (p. 52).

Geographical
Distribution.—Cosmopolitan. In most countries the majority
of the freshwater sponges belong to this genus, but in Japan
Ephydatia seems to predominate.

Key to the Indian Species of Spongilla.

[Pg
69]

Subgenus A. EUSPONGILLA,
Vejdovsky.

Type, Spongilla lacustris,
auctorum.

Spongillæ in which the gemmules are covered with a thick, apparently
granular pneumatic coat. A delicate membrane often occurs outside this
coat, but it is never thick or horny. The gemmules usually lie free in
the sponge but sometimes adhere to its support; rarely they are fastened
together in groups (e. g. in S. aspinosa, Potts). The
skeleton-spicules are never very stout and the skeleton is always
delicate.

The species in this subgenus are closely allied and must be
distinguished rather by the sum of their peculiarities than by any one
character. They occur in all countries in which Spongillidæ are found.
Seven Indian species may be recognized.

1. Spongilla lacustris, auctorum.

[I have not attempted to give a detailed synonymy
of this common species. There is no means of telling whether many of the
earlier names given to forms or allies of S. lacustris are actual
synonyms, and it would serve no useful purpose, so far as the fauna of
India is concerned, to complicate matters by referring to obscure
descriptions or possible descriptions of a species only represented in
India, so far as we know, by a specialized local race, to which separate
references are given.]

Sponge soft and easily compressed, very brittle when dry,
usually consisting of a flat or rounded basal portion of no great depth
and of long free cylindrical branches, which droop when removed from the
water; branches occasionally absent. Colour bright green when the sponge
is growing in a strong light, dirty flesh-colour when it is growing in
the shade. (Even in the latter case[Pg 70] traces of the "green
corpuscles" can be detected in the cells of the parenchyma.) Oscula
star-shaped, of moderate size, as a rule rendered conspicuous by the
furrows that radiate from them over the outer surface of the parenchyma
below the external membrane; oscular collars well developed.

Skeleton reticulate, loose, with definite radiating and
transverse fibres held together by a small quantity of spongin; the
fibres slender but not extremely so.

Spicules. Skeleton-spicules smooth, sharply pointed, long,
slender. Flesh-spicules slender, covered with small spines, sharply
pointed, nearly straight. Gemmule-spicules resembling the flesh-spicules
but shorter and as a rule more strongly curved, sometimes bent so as to
form semicircular figures, usually pointed somewhat abruptly; their
spines relatively longer than those of the flesh-spicules, often curved
backwards, especially near the ends of the spicules, at which points
they are often longer than elsewhere.

Gemmules usually numerous in autumn, lying free in the sponge,
spherical, variable in size but usually rather large, as a rule covered
with a thick granular coat in which the spicules are arranged
tangentially; a horizontal layer of spicules often present in the
external membrane; the granular coat and its spicules occasionally
deficient. No foraminal tubule; its place sometimes taken by an open,
bowl-shaped chitinous structure the base of which is in continuity with
the inner chitinous coat of the gemmule.

S. lacustris is an extremely variable species, varying in the
size, proportions and shape of its spicules, in its external form and in
the size and structure of the gemmule. A considerable number of
varieties have been described from different parts of Europe and N.
America, but some of these may represent distinct but closely-allied
species; descriptions of most of them will be found in Potts's
"Fresh-Water Sponges." The embryology and the earlier stages of the
development from the egg have been described in great detail by Evans
(Quart. J. Micr. Sci. (n. s.) xlii, p. 363 (1899)), while the anatomy
and physiology are discussed by most authors who have written on these
features in the Spongillidæ.

Type.—It is impossible to say who
was the first authority to use the name Spongilla lacustris in
the sense in which it is used by recent authors. No type can therefore
be recognized.

Geographical Distribution.—S.
lacustris occurs all over Europe and N. America and is probably the
commonest species in most parts of both continents. It has also been
found in Northern Asia and may occur in the Himalayan lakes and in the
north-west of India.

[Pg
71]1 a. Subspecies reticulata*,
Annandale.

This race differs from the typical S. lacustris in the
following particulars:—

(1) The branches are always compressed and
anastomose freely when well developed (fig. 5, p. 37);

(2) the skeleton-fibres are finer;

(3) the skeleton-spicules are longer;

(4) the gemmule-spicules are longer and more slender
and are never strongly bent.

As regards the form of the skeleton- and gemmule-spicules and also
that of the branches the subspecies reticulata resembles S.
alba rather than S. lacustris, but owing to the fact that it
agrees with S. lacustris in its profuse production of branches,
in possessing green corpuscles and in its fragility, I think it should
be associated with that species.

Fig. 8.

A=gemmule-spicules of Spongilla lacustris
subsp. reticulata (from type); B=gemmule-spicules of S.
alba from Calcutta: both highly magnified.

The branches are sometimes broad (fig. 5, p. 37), sometimes very
slender. In the latter condition they resemble blades of grass growing
in the water.

Type in the Indian Museum; a co-type in
the British Museum.

[Pg 72]Geographical
Distribution.—All over Eastern India and Burma; also in the
Bombay Presidency. Localities:—Bengal, Port Canning, Ganges delta; Rajshahi
(Rampur Bhulia) on the Ganges, 150 miles N. of Calcutta
(Annandale); Puri district, Orissa (Annandale); R. Jharai,
Siripur, Saran district, Tirhut (M. Mackenzie): Madras Presidency, Madras (town) (J. R.
Henderson): Bombay Presidency, Igatpuri,
W. Ghats (Annandale).

Biology.—This subspecies is usually
found in small masses of water, especially in pools of rain-water, but
Mr. Mackenzie found it growing luxuriantly in the Jharai at a time of
flood in September. It is very abundant in small pools among the
sand-dunes that skirt the greater part of the east coast of India. Here
it grows with great rapidity during the "rains," and often becomes
desiccated even more rapidly as soon as the rain ceases. As early in the
autumn as October I have seen masses of the sponge attached, perfectly
dry, to grass growing in the sand near the Sur Lake in Orissa. They
were, of course, dead but preserved a life-like appearance. Some of them
measured about six inches in diameter. At Port Canning the sponge grows
during the rains on the brickwork of bridges over ditches of brackish
water that dry up at the beginning of winter, while at Rajshahi and at
Igatpuri I found it at the edges of small ponds, at the latter place in
November, at the former in February. Specimens taken at Madras by Dr.
Henderson during the rains in small ponds in the sand contained no
gemmules, but these structures are very numerous in sponges examined in
autumn or winter.

Numerous larvæ of Sisyra indica (p. 92) were found in this
sponge at Rajshahi. Unlike those obtained from S. alba, they had
a green colour owing to the green matter sucked from the sponge in their
stomachs. The coralloides phase of Plumatella fruticosa
(p. 219) was also found in S. lacustris subsp. reticulata
at Rajshahi.

So far as my experience goes, this subspecies has always a bright
green colour due to the presence of "green corpuscles," even when it is
growing in a pond heavily shaded by trees or under the arch of a small
bridge. Probably the more intense light of India enables the corpuscles
to flourish in situations in which in Europe they would lose their
chlorophyll.

2. Spongilla proliferens*, Annandale.

Sponge forming soft, shallow cushions rarely more than 10 cm.
in diameter on the leaves of water-plants, or small irregular masses on
their roots and stems. Colour bright green. Oscula[Pg 73]
moderate, flat, surrounded by deep, cone-shaped collars; radiating
furrows and canals in the parenchyma surrounding them often deep.
External pores contained normally in single cells. The surface
frequently covered by small rounded buds; true branches if present more
or less flattened or conical, always short, as a rule absent.

Skeleton loose, feebly reticulate at the base of the sponge;
transverse fibres slender in the upper part of the sponge, often
scarcely recognizable at its base. Very little spongin present.

Spicules. Skeleton-spicules long, smooth, sharply pointed; the
length on an average at least 20 times the greatest breadth, often more.
Flesh-spicules slender, gradually pointed, nearly straight, covered with
minute straight or nearly straight spines. Gemmule-spicules very
similar, but usually a little stouter and often blunt at the ends; their
spines rather longer than those on the flesh-spicules, usually more
numerous near the ends than in the middle of the spicule, slightly
retroverted, those at the extreme tips often so arranged as to suggest a
rudimentary rotule.

Fig. 9.—Gemmule of Spongilla proliferens
as seen in optical section (from Calcutta), × 140.

Gemmules usually numerous, lying free near the base of the
sponge, very variable in size, spherical, surrounded by a thick granular
layer in which the spicules, which are always very numerous, are
arranged tangentially, their position being more near the vertical than
the horizontal; a few horizontal spicules usually present on the
external surface of the gemmule, which frequently has a ragged
appearance owing to some of the tangential spicules protruding further
than others. Foraminal tubule stout, cylindrical, usually somewhat
contorted; its orifice irregular in outline. Sometimes more than one
foramen present.

[Pg
74]S. proliferens can be distinguished from all forms
of S. lacustris and S. alba by the fact that its gemmules
possess a foraminal tubule; from S. cinerea it can be
distinguished by its colour and its smooth skeleton-spicules, and from
S. travancorica by its free gemmules. I have been enabled by the
kindness of Prof. Max Weber to examine specimens from Celebes and Java
identified by him as S. cinerea, Carter, and have no doubt that
they belong to my species.

Type in the Indian Museum; a co-type in
the British Museum.

Geographical Distribution.—All over
Eastern India and Burma; also in Cochin on the west coast; Ceylon; W.
China; Java, Flores and Celebes. Localities:—Bengal, Calcutta and neighbourhood
(Annandale); Berhampore, Murshidabad district (R. E.
Lloyd): Assam, Mangal-dai near the Bhutan
frontier (S. W. Kemp): Madras
Presidency, Madras (town) and neighbourhood (J. R.
Henderson); Rambha, Ganjam district (Annandale); Bangalore,
Mysore (alt. ca. 3000 ft.) (Annandale); Ernakulam and
Trichur, Cochin (G. Mathai): Burma,
Rangoon (Annandale, J. Coggin Brown); Prome, Upper Burma
(J. Coggin Brown); Kawkareik, Amherst district, Tenasserim
(Annandale): Ceylon, between
Maradankawela and Galapita-Gala, North Central Province (Willey).
Mr. J. Coggin Brown has recently brought back specimens from Yunnan.

Biology.—S. proliferens is
usually found in ponds which never dry up; Prof. Max Weber found it in
small streams in Malaysia. It is common in India on the leaves of
Vallisneria and Limnanthemum, on the roots of Pistia
stratiotes and on the stems of rushes and grass. So far as I have
been able to discover, the life of the individual sponge is short, only
lasting a few weeks.

Sexual reproduction occurs seldom or never, but reproduction by means
of buds and gemmules continues throughout the year. The former is a rare
method of reproduction in most Spongillidæ but in this species occurs
normally and constantly, the buds being often very numerous on the
external surface. They arise a short distance below the surface as
thickenings in the strands of cells that accompany the radiating fibres
of the skeleton. As they grow they push their way up the fibres, forcing
the external membrane outwards. The membrane contracts gradually round
their bases, cuts off communication between them and the parent sponge
and finally sets them adrift. No hole remains when this takes place, for
the membrane closes up both round the base of the bud and over the
aperture whence it has emerged.

The newly liberated bud already possesses numerous minute pores, but
as yet no osculum; its shape exhibits considerable variation, but the
end that was farthest from the parent-sponge before liberation is always
more or less rounded, while the other end is flat. The size also varies
considerably. Some of the buds float, others sink. Those that float do
so either owing to their[Pg 75] shape, which depends on the degree of
development they have reached before liberation, or to the fact that a
bubble of gas is produced in their interior. The latter phenomenon only
occurs when the sun is shining on the sponge at the moment they are set
free, and is due to the action of the chlorophyll of the green bodies so
abundant in certain of the parenchyma cells of this species. If the
liberation of the bud is delayed rather longer than usual, numbers of
flesh-spicules are produced towards the ends of the primary
skeleton-fibres and spread out in one plane so as to have a fan-like
outline; in such buds the form is more flattened and the distal end less
rounded than in others, and the superficial area is relatively great, so
that they float more readily. Those buds that sink usually fall in such
a way that their proximal, flattened end comes in contact with the
bottom or some suspended object, to which it adheres. Sometimes,
however, owing to irregularity of outline in the distal end, the
proximal end is uppermost. In this case it is the distal end that
adheres. Whichever end is uppermost, it is in the uppermost end, or as
it may now be called, the upper surface, that the osculum is formed.
Water is drawn into the young sponge through the pores and, finding no
outlet, accumulates under the external membrane, the subdermal cavity
being at this stage even larger than it is in the adult sponge.
Immediately after adhesion the young sponge flattens itself out. This
process apparently presses together the water in the subdermal cavity
and causes a large part of it to accumulate at one point, which is
usually situated near the centre of the upper surface. A transparent
conical projection formed of the external membrane arises at this point,
and at the tip of the cone a white spot appears. What is the exact cause
of this spot I have not yet been able to ascertain, but it marks the
point at which the imprisoned water breaks through the expanded
membrane, thus forming the first osculum. Before the aperture is formed,
it is already possible to distinguish on the surface of the parenchyma
numerous channels radiating from the point at which the osculum will be
formed to the periphery of the young sponge. These channels as a rule
persist in the adult organism and result from the fact that the inhalent
apertures are situated at the periphery, being absent from both the
proximal and the distal ends of the bud. In the case of floating buds
the course of development is the same, except that the osculum, as in
the case of development from the gemmule in other species (see Zykoff,
Biol. Centrbl. xii, p. 713, 1892), is usually formed before adhesion
takes place.

The sponge of S. proliferens is usually too small to afford
shelter to other animals, and I have not found in it any of those
commonly associated with S. carteri and S. alba.

Owing to its small size S. proliferens is more easily kept
alive in an aquarium than most species, and its production of buds can
be studied in captivity. In captivity a curious[Pg 76] phenomenon is manifested,
viz. the production of extra oscula, often in large numbers. This is due
either to a feebleness in the currents of the sponge which makes it
difficult to get rid of waste substances or to the fact that the canals
get blocked. The effluent water collects in patches under the external
membrane instead of making its way out of the existing oscula, and new
oscula are formed over these patches in much the same way as the first
osculum is formed in the bud.

3. Spongilla alba*, Carter.

Sponge forming masses of considerable area, but never of more
than moderate depth or thickness. Surface smooth and undulating or with
irregular or conical projections; sponge hard but brittle; colour white
or whitish; oscula of moderate or large size, never very conspicuous;
radiating furrows absent or very short; external membrane adhering to
the substance of the sponge.

Skeleton forming a moderately dense network of slender
radiating and transverse fibres feebly held together; little spongin
present; the meshes much smaller than in S. lacustris or S.
proliferens.

Spicules. Skeleton-spicules smooth, sharply pointed, slender,
feebly curved. Gemmule-spicules (fig. 8, p. 71) slender, cylindrical,
blunt or abruptly pointed at the ends, feebly curved, bearing relatively
long backwardly directed spines, which are usually more numerous at the
ends than near the middle of the shaft. Flesh-spicules very numerous in
the parenchyma and especially the external membrane, as a rule
considerably more slender and more sharply pointed than the
gemmule-spicules, covered with straight spines which are often longer at
the middle of the shaft than at the ends.

Gemmules usually of large size, with a moderately thick granular
layer; spicules never very numerous, often lying horizontally on the
external surface of the gemmule as well as tangentially in the granular
layer; no foraminal tubule; a foraminal cup sometimes present.

3a. Var. cerebellata, Bowerbank.

This variety is distinguished from the typical form by the total
absence of flesh-spicules. The gemmule-spicules are also more numerous
and cross one another more regularly.

3b. Var. bengalensis*, Annandale. (Plate I, figs. 1-3.)

The sponge is either devoid of branches or produces irregular,
compressed, and often digitate processes, sometimes of considerable
length and delicacy. Flesh-spicules are usually present throughout the
sponge, but are sometimes absent from one part of a specimen and present
in others. Some of the gemmules are often much smaller than the others.
Perhaps this form should be regarded as a phase rather than a true
variety (see p. 18).

All forms of S. alba can be distinguished from all forms of
S. lacustris by the much closer network of the skeleton and by
the consequent hardness of the sponge; also by the complete absence of
green corpuscles.

Types. The types of the species and of the
var. cerebellata are in the British Museum, with fragments of the
former in the Indian Museum; that of var. bengalensis is in the
Indian Museum, with a co-type in London.

Geographical Distribution.—India and
Egypt. Localities:—Bombay
Presidency, island of Bombay (Carter); Igatpuri, W. Ghats
(Annandale): Bengal, Calcutta; Port
Canning, Ganges delta (var. bengalensis) (Annandale);
Garia, Salt Lakes, nr. Calcutta (var. bengalensis) (B. L.
Chaudhuri); Chilka Lake, Orissa (var. bengalensis) (Gopal
Chunder Chatterjee): Madras Presidency,
Rambha, Ganjam district (Annandale): Nizam's
Territory, Aurangabad (Bowerbank, var.
cerebellata). The var. cerebellata has also been taken
near Cairo.

Biology.—The typical form of the
species is usually found growing on rocks or bricks at the edges of
ponds, while the variety bengalensis abounds on grass-roots in
pools and swamps of brackish water in the Ganges delta and has been
found on mussel-shells (Modiola jenkinsi, Preston) in practically
salt water in the Chilka Lake. Carter procured the typical form at
Bombay on stones which were only covered for six months in the year, and
"temporarily on floating objects." In Calcutta this form flourishes in
the cold weather on artificial stonework in the "tanks" together with
S. carteri, S. fragilis, Ephydatia meyeni, and
Trochospongilla latouchiana.

The variety bengalensis is best known to me as it occurs in
certain ponds of brackish water at Port Canning on the Mutlah River,
which connects the Salt Lakes near Calcutta with the sea.[Pg 78] It
appears in these ponds in great luxuriance every year at the beginning
of the cold weather and often coats the whole edge for a space of
several hundred feet, growing in irregular masses which are more or less
fused together on the roots and stems of a species of grass that
flourishes in such situations. Apparently the tendency for the sponges
to form branches is much more marked in some years than in others (see
Pl. I, figs. 1-3). The gemmules germinate towards the end of the
"rains," and large masses of sponge are not formed much before December.
At this season, however, the level of the water in the ponds sinks
considerably and many of the sponges become dry. If high winds occur,
the dry sponges are broken up and often carried for considerable
distances over the flat surrounding country. In January the gemmules
floating on the surface of the ponds form a regular scum. S. alba
var. bengalensis is the only sponge that occurs in these ponds at
Port Canning, but S. lacustris, subsp. reticulata, is
occasionally found with it on brickwork in the ditches that drain off
the water from the neighbouring fields into the Mutlah estuary. The
latter sponge, however, perishes as these ditches dry up, at an earlier
period than that at which S. alba reaches its maximum
development.

The larvæ of Sisyra indica are commonly found in the oscula of
the typical form of S. alba as well as in those of S.
lacustris subsp. reticulata, and S. carteri; but the
compact structure of the sponge renders it a less suitable residence for
other incolæ than S. carteri.

In the variety bengalensis, as it grows in the ponds at Port
Canning, a large number of arthropods, molluscs and other small animals
take shelter. Apart from protozoa and rotifers, which have as yet been
little studied, the following are some of the more abundant inhabitants
of the sponge:—The sea-anemone, Sagartia schilleriana
subsp. exul (see p. 140), which frequently occurs in very
large numbers in the broader canals; the free-living nematode,
Oncholaimus indicus^[W], which makes its
way in and out of the oscula; molluscs belonging to several species of
the genus Corbula, which conceal themselves in the canals but are
sometimes engulfed in the growing sponge and so perish; young
individuals of the crab Varuna litterata, which hide among the
branches and ramifications of the larger sponges together with several
small species of prawns and the schizopod Macropsis orientalis^[X]; the peculiar amphipod Quadrivisio bengalensis^[Y], only known from the ponds at Port
Canning, which breeds in little communities inside the sponge; a small
isopod^[Z], allied to[Pg 79] Sphæroma walkeri,
Stebbing; the larva of a may-fly, and those of at least two midges
(Chironomidæ).

The peculiarly mixed nature (marine and lacustrine) of the fauna
associated with S. alba in the ponds at Port Canning is well
illustrated by this list, and it only remains to be stated that little
fish (Gobius alcockii, Barbus stigma, Haplochilus
melanostigma, H. panchax, etc.) are very common and feed
readily on injured sponges. They are apparently unable to attack a
sponge so long as its external membrane is intact, but if this membrane
is broken, they swarm round the sponge and devour the parenchyma
greedily. In fresh water one of these fishes (Gobius alcockii,
see p. 94) lays its eggs in sponges.

The chief enemy of the sponges at Port Canning is, however, not an
animal but a plant, viz., a green filamentous alga which grows inside
the sponge, penetrating its substance, blocking up its canals and so
causing it to die. Similar algæ have been described as being beneficial
to the sponges in which they grow^[AA], but my experience is that they are
deadly enemies, for the growth of such algæ is one of the difficulties
which must be fought in keeping sponges alive in an aquarium. The alga
that grows in S. alba often gives it a dark green colour, which
is, however, quite different from the bright green caused by the
presence of green corpuscles. The colour of healthy specimens of the
variety bengalensis is a rather dark grey, which appears to be
due to minute inorganic particles taken into the cells of the parenchyma
from the exceedingly muddy water in which this sponge usually grows. If
the sponge is found in clean water, to whichever variety of the species
it belongs, it is nearly white with a slight yellowish tinge. Even when
the typical form is growing in close proximity to S. proliferens,
as is often the case, no trace of green corpuscles is found in its
cells.

4. Spongilla cinerea*, Carter.

Sponge forming large, flat sheets, never more than a few
millimetres in thickness, without a trace of branches, compact but very
friable, of a dark greyish colour; oscula small and inconspicuous or
moderately large, never prominent; membrane adhering closely to the
sponge.

Skeleton with well-defined but slender radiating fibres, which
contain very little spongin; transverse fibres close together but
consisting for the most part of one or two spicules only.

[Pg
80]Spicules. Skeleton-spicules short, slender, sharply
pointed, minutely serrated or irregular in outline, almost straight.
Gemmule-spicules very small, rather stout, cylindrical, pointed, covered
with relatively long and stout spines which are either straight or
directed towards the ends of the spicule. Flesh-spicules fairly numerous
in the external membrane but by no means abundant in the parenchyma,
very slender, gradually pointed, covered uniformly with minute but
distinct spines.

Gemmules very small, only visible to the naked eye as minute
specks, as a rule numerous, free in the substance of the sponge, each
provided with a slender foraminal tubule and covered with a thick
granular coat in which the gemmule-spicules are arranged almost
horizontally; a horizontal layer of spicules also present on the
external surface of the gemmule; gemmule-spicules very numerous.

Fig. 10.—Gemmules and fragment of the skeleton
of Spongilla cinerea (from type specimen), × 35.

This sponge is easily distinguished from its Indian allies by the
form of its skeleton-spicules, which are, as Bowerbank expresses it,
"subspined"; that it to say, under a high power of the microscope their
outline appears to be very minutely serrated, although under a low power
they seem to be quite smooth. The spicules also are smaller than those
of S. alba, the only species with which S. cinerea is
likely to be confused, and the gemmule has a well-developed foraminal
tubule; the skeleton is much closer than in S. proliferens.

Type in the British Museum; a piece in the
Indian Museum.

Geographical Distribution.—S.
cinerea is only known from the Bombay Presidency. Carter obtained
the original specimens at Bombay and the only ones I have found were
collected at Nasik, which is situated on the eastern slopes of the
Western Ghats, about 90 miles to the north-east.

Biology.—Carter's specimens were
growing on gravel, rocks and stones at the edge of "tanks," and were
seldom covered for more than six months in the year. Mine were on the
sides of a[Pg
81] stone conduit built to facilitate bathing by conveying a
part of the water of the Godaveri River under a bridge. They were
accompanied by Spongilla indica and Corvospongilla
lapidosa (the only other sponges I have found in running water in
India) and in the month of November appeared to be in active growth.

5. Spongilla travancorica*, Annandale.

Sponge small, encrusting, without branches, hard but brittle;
its structure somewhat loose; colour dirty white. Dermal membrane in
close contact with the skeleton; pores and oscula inconspicuous. Surface
minutely hispid, smooth and rounded as a whole.

Skeleton consisting of moderately stout and coherent radiating
fibres and well-defined transverse ones; a number of horizontal
megascleres present at the base and surface, but not arranged in any
definite order. No basal membrane.

Fig. 11.—Microscleres of Spongilla
travancorica. A=Gemmule-spicules; B=flesh-spicules (from type
specimen), × 240.

Spicules. Skeleton-spicules smooth, pointed at either end,
moderately stout, straight or curved, sometimes angularly bent;
curvature usually slight. Free microscleres abundant in the dermal
membrane, slender, nearly straight, gradually and sharply pointed,
profusely ornamented with short straight spines, which are much more
numerous and longer at the middle than near the ends. Gemmule-spicules
stouter and rather longer, cylindrical, terminating at each end in a
sharp spine, ornamented with shorter spines, which are more numerous and
longer at the ends than at the middle; at the ends they are sometimes
directed backwards, without, however, being curved.

Gemmules firmly adherent to the support of the sponge, at the
base of which they form a layer one gemmule thick; each provided with at
least one foraminal tubule, which is straight and conical: two tubules,
one at the top and one at one side, usually present. Granular layer well
developed. Spicules arranged irregularly in this layer, as a rule being
more nearly vertical than horizontal but pointing in all directions, not
confined externally by a membrane; no external layer of horizontal
spicules.

[Pg
82]

Measurements of Spicules and Gemmules.

This species is easily distinguished from its allies of the subgenus
Euspongilla by its adherent gemmules with their (usually)
multiple apertures and rough external surface.

Type in the collection of the Indian
Museum.

Habitat. Backwater near Shasthancottah,
Travancore, in slightly brackish water; on the roots of shrubs growing
at the edge; November, 1908 (Annandale).

The specimens were dead when found.

6. Spongilla hemephydatia*, Annandale.

Fig. 12.—Gemmule and spicules of Spongilla
hemephydatia (from type specimen).

Sponge soft, fragile, amorphous, of a dirty yellow colour,
with large oscula, which are not conspicuously raised above the[Pg 83]
surface but open into very wide horizontal channels in the substance of
the sponge. The oscular collars are fairly well developed, but the
subepidermal space is not extensive.

Skeleton diffuse, consisting of very fine radiating fibres,
which are crossed at wide and irregular intervals by still finer
transverse ones; very little chitinoid substance present.

Spicules. Skeleton-spicules smooth, slender, sharply pointed
at both ends, nearly straight. No true flesh-spicules. Gemmule-spicules
straight or nearly so, cylindrical, or constricted in the middle,
obscurely pointed or blunt, clothed with short, sharp, straight spines,
which are very numerous but not markedly longer at the two ends; these
spicules frequently found free in the parenchyma.

Gemmules numerous, small, free, spherical, yellow, with a
well-developed granular coat (in which the spicules are arranged almost
horizontally) and external to it a fine membrane which in preserved
specimens becomes puckered owing to unequal contraction; each gemmule
with a single aperture provided with a straight, rather wide, but very
delicate foraminal tubule.

Measurements of Spicules and Gemmules.

This sponge in its general structure bears a very close resemblance
to Spongilla crateriformis.

Type in the collection of the Indian
Museum.

Habitat. Growing on weeds at the edge of
the Sur Lake, Orissa, October 1908. Only one specimen was taken,
together with many examples of S. lacustris subsp.
reticulata, S. carteri and S. crassissima.

7. Spongilla crateriformis* (Potts).

[Pg
84]Sponge very fragile, forming soft irregular masses
on the roots and stems of water-plants, between which it is sometimes
stretched as a delicate film, or thin layers or cushions on flat
surfaces. Oscula large, flat, circular, or of irregular shape, opening
into broad horizontal canals, which at their distal end are superficial
and often covered by the external membrane only. Colour white,
yellowish, greyish, or blackish.

Skeleton very delicate; radiating fibres rarely consisting of
more than two parallel spicules; transverse fibres far apart, frequently
consisting of single spicules; very little spongin present.

Fig. 13.—Spicules of Spongilla
crateriformis.

A. From specimen taken in July in a tank on the
Calcutta maidan. B. From type specimen of Ephydatia indica taken
in the Indian Museum tank in winter. Both figures × 240.

Spicules. Skeleton-spicules feebly curved, slender, as a rule
irregular in outline, sometimes almost smooth; the ends as a rule
sharply pointed, often constricted off and expanded so as to resemble
spear-heads, occasionally blunt. No true flesh-spicules.
Gemmule-spicules often free in the parenchyma, cylindrical, slender,
very variable in length in different sponges, straight or nearly so, as
a rule with an irregular circle of strong straight or recurved spines at
either end resembling a rudimentary rotule, and with shorter straight
spines scattered on the shaft, sometimes without the rudimentary rotule,
either truncate at the ends or terminating in a sharp spine.

Gemmules small, free, each surrounded by a thick granular
layer in which the spicules stand upright or nearly so, and covered
externally by a delicate but very distinct chitinous membrane; no[Pg 85]
horizontal spicules; foramen situated at the base of a crater-like
depression in the granular coat, which is sometimes raised round it so
as to form a conspicuous rampart; a short, straight foraminal
tubule.

The shape of the spicules is extremely variable, and sponges in which
they are very different occur in the same localities and even in the
same ponds. It is possible that the differences are directly due to
slight changes in the environment, for in one pond in Calcutta a form
with Spongilla-like gemmule-spicules appears to replace the
typical form, which is common in winter, during the hot weather and
"rains." I have not, however, found this to be the case in other ponds.
Perhaps S. hemephydatia will ultimately prove to be a variety of
this very variable species, but its smooth and regular skeleton-spicules
and short-spined gemmule-spicules afford a ready method of
distinguishing it from S. crateriformis. The two sponges are
easily distinguished from all others in the subgenus Euspongilla
by the upright and regular arrangement of their gemmule-spicules, for
although in S. proliferens and S. travancorica some of the
gemmule-spicules are nearly vertical, their arrangement is always
irregular, a large proportion of the spicules make an acute angle with
the inner coat of the gemmule and a few as a rule lie parallel to it.
The systematic position of S. crateriformis is almost exactly
intermediate between Euspongilla and Ephydatia, to which
genus it has hitherto been assigned. I think, however, that taking into
consideration its close relationship to S. hemephydatia, it is
best to assign it to Spongilla, as its rudimentary rotules never
form distinct disks. I have examined some of Potts's original specimens
from different American localities and can detect no constant difference
between them and Indian specimens.

Types in the United States National
Museum; co-types in Calcutta.

Geographical Distribution.—This
sponge was originally described from North America (in which continent
it is widely distributed) and has been recorded from the west of Ireland
with some doubt. In India and Burma it is widely distributed. Bengal, Calcutta and neighbourhood
(Annandale); Sonarpur, Gangetic delta (Annandale); Bombay Presidency, Igatpuri Lake, W. Ghats
(altitude ca. 2,000 feet) (Annandale); Madras Presidency, neighbourhood of Madras town
(J. R. Henderson); Museum compound, Egmore (Madras town)
(Annandale); near Bangalore (alt. ca. 3,000 ft.), Mysore
State (Annandale); Ernakulam, Cochin (G. Mathai): Burma, Kawkareik, interior of Amherst district,
Tenasserim, and the Moulmein waterworks in the same district
(Annandale).^[AB]

[Pg
86]Biology.—S.
crateriformis flourishes in Calcutta throughout the year. Here it is
usually found adhering to the roots of water-plants, especially
Pistia and Limnanthemum. In the case of the former it
occurs at the surface, in that of the latter at the bottom. When growing
near the surface or even if attached to a stone at the bottom in clear
water, it is invariably of a pale yellowish or greyish colour. When
growing on the roots of Limnanthemum in the mud of the Gangetic
alluvium, however, it is almost black, and when growing in the reddish
muddy waters of the tanks round Bangalore of a reddish-brown colour.
This appears to be due entirely to the absorption of minute particles of
inorganic matter by the cells of the parenchyma. If black sponges of the
species are kept alive in clean water, they turn pure white in less than
a week, apparently because these particles are eliminated. When growing
on stones the sponge, as found in India, often conforms exactly with
Potts's description: "a filmy grey sponge, branching off here and there
... yet with a curious lack of continuity...."

The wide efferent canals of this sponge afford a convenient shelter
to small crustacea, and the isopod Tachæa spongillicola, Stebbing
(see p. 94), is found in them more abundantly than in those of any
other sponge. This is especially the case when the sponge is growing at
the bottom. On the surface of the sponge I have found a peculiar
protozoon which resembles the European Trichodina spongillæ in
general structure but belongs, I think, to a distinct species, if not to
a distinct genus.

Subgenus B. EUNAPIUS, J. E. Gray.

Type, Spongilla carteri, Carter.

Spongillæ in which the gemmules are covered with layers of distinct
polygonal air-spaces with chitinous walls.

The gemmules are usually fastened together in groups, which may
either be free in the sponge or adhere to its support as a "pavement
layer"; sometimes, however, they are not arranged in this manner, but
are quite independent of one another. The skeleton is usually delicate,
sometimes very stout (e. g., in S. nitens,
Carter).

The term Eunapius here used is not quite in the original
sense, for Gray included under it Bowerbank's Spongilla
paupercula which is now regarded as a form of S. lacustris.
His description, nevertheless, fits the group of species here associated
except in one particular, viz., the smoothness of the gemmule-spicules
to which he refers, for this character, though a feature of S.
carteri, is not[Pg 87] found in certain closely allied forms.
The use of "Spongilla" in a double sense may be avoided by the
adoption of Gray's name.

The subgenus Eunapius is, like Euspongilla,
cosmopolitan. It is not, however, nearly so prolific in species. Four
can be recognized in India, two of which range, in slightly different
forms, as far north as Europe, one of them also being found in North
America, Northern Asia, and Australia.

8. Spongilla carteri* Carter
(Bowerbank, in litt.). (Plate II. fig.
1.)

Fig. 14.—Gemmule of Spongilla carteri
(from Calcutta), as seen in optical section, × 140.

Sponge massive, as a rule with the surface smooth and rounded,
occasionally bearing irregular ridges, which may even take the form of
cockscombs; the oscula large, rounded, conspicuous but not raised above
the surface of the sponge, leading into broad vertical[Pg 88]
canals; the lateral canals, except in the immediate vicinity of the
central vertical ones, not very broad; the oscular collars extending for
a considerable distance over the oscula in living or well-preserved
specimens, never standing out from the surface; the oscula never
surrounded by radiating furrows. The inhalent pores surrounded
externally by unmodified cells of the external membrane. Colour greyish,
sometimes with a flush of green on the external surface.

The sponge has a peculiarly strong and offensive smell.

Skeleton fairly compact, with well-developed radiating fibres;
the transverse fibres splayed out at either end so that they sometimes
resemble a pair of fans joined together by the handles (fig. 3,
p. 33). A moderate amount of spongin present.

Spicules. Skeleton-spicules smooth, pointed, nearly straight,
never very stout but somewhat variable in exact proportions.
Gemmule-spicules similar but much smaller. (There are no true
flesh-spicules, but immature skeleton-spicules may easily be mistaken
for them.)

Gemmules as a rule numerous, spherical or flattened at the
base, variable in size, each covered by a thick coat consisting of
several layers of relatively large polygonal air-spaces. A single
aperture surrounded by a crater-like depression in the cellular coat and
provided with a foraminal tubule resembling an inverted bottle in shape.
(This tubule, which does not extend beyond the surface of the cellular
coat, is liable to be broken off in dried specimens.) The spicules
variable in quantity, arranged irregularly among the spaces of the
cellular coat and usually forming a sparse horizontal layer on its
external surface. Each gemmule contained in a cage of skeleton-spicules,
by the pressure of which it is frequently distorted.

8a. Var. mollis*, nov.

This variety is characterized by a paucity of skeleton-spicules. The
sponge is therefore soft and so fragile that it usually breaks in pieces
if lifted from the water by means of its support. Owing to the paucity
of skeleton-spicules, which resemble those of the typical form
individually, the radiating and transverse fibres are extremely
delicate.

Common in Calcutta.

8b. Var. cava*, nov.

This variety is characterized by the fact that the oscula open into
broad horizontal canals, the roof of which is formed by a thin layer of
parenchyma and skeleton or, in places, of the external membrane only.
The skeleton is loose and fragile, and the living sponge has a peculiar
glassy appearance. In spirit the colour is yellowish, during life it is
greenish or white.

Taken at Bombay; November, 1907.

[Pg
89]8c. Var. lobosa*, nov.

The greater part of the sponge in this variety consists of a number
of compressed but pointed vertical lobes, which arise from a relatively
shallow, rounded base, in which the oscula occur. The dried sponge has a
yellowish colour.

Apparently common in Travancore.

* * * * *

I cannot distinguish these three "varieties"^[AC] from the typical form as distinct
species; indeed, their status as varieties is a little doubtful in two
cases out of the three. Var. cava appears to be a variety in the
strict sense of the word (see p. 18), for it was found on the
island of Bombay, the original locality of the species, growing side by
side with the typical form. Var. lobosa, however, should perhaps
be regarded as a subspecies rather than a variety, for I have received
specimens from two localities in the extreme south-west of India and
have no evidence that the typical form occurs in that part of the
country. Evidence, however, is rather scanty as regards the occurrence
of freshwater sponges in S. India. Var. mollis, again, may be a
phase directly due to environment. It is the common form in the ponds of
certain parts (e. g. in the neighbourhood of the Maidan and
at Alipore) of the Calcutta municipal area, but in ponds in other parts
(e. g. about Belgatchia) of the same area, only the typical
form is found. It is possible that the water in the former ponds may be
deficient in silica or may possess some other peculiarity that renders
the production of spicules difficult for S. carteri; but this
seems hardly probable, for S. crassissima, a species with a
rather dense siliceous skeleton, flourishes in the same ponds. I have
noticed that in ponds in which the aquatic vegetation is luxuriant and
such genera of plants as Pistia and Limnanthemum flourish,
there is always a tendency for S. carteri to be softer than in
ponds in which the vegetation is mostly cryptogamic, and in Calcutta
those parts of the town in which sponges of this species produce most
spicules are those in which a slight infiltration of brackish water into
the ponds may be suspected; but in the interior of India, in places
where the water is absolutely fresh, hard specimens seem to be the rule
rather than the exception.

S. carteri is closely related to S. nitens, Carter
(Africa, and possibly S. America), but differs from that species in its
comparatively slender, sharp skeleton-spicules and smooth
gemmule-spicules. It may readily be distinguished from all other Indian
freshwater sponges by its large, deep, round oscula, but this feature is
not so marked in var. lobosa as in the other forms. The typical
form and[Pg
90] var. mollis grow to a larger size than is recorded
for any other species of the family. I possess a specimen of the typical
form from the neighbourhood of Calcutta which measures 30 × 27 cm. in
diameter and 19.5 cm. in depth, and weighs (dry) 24-3/4 oz. The base of
this specimen, which is solid throughout, is nearly circular, and the
general form is mound-shaped. Another large specimen from Calcutta is in
the form of an irregular wreath, the greatest diameter of which is 34
cm. This specimen weighs (dry) 16-1/4 oz. Both these specimens probably
represent the growth of several years.