10. _S. gemina_*, sp. nov.

11. _S. cra.s.sissima_*, Annandale (1907).

11_a_. _S. cra.s.sissima_ var. _cra.s.sior_*, 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).

15_a_. _P. aurea_ var. _subspinosa_*, nov.

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).

Order HALICHONDRINA.

Siliceous monaxon sponges in which the h.o.r.n.y 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 SPONGILLIDae.

SPONGILLADae, 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 a.s.sociated with the gemmule sometimes consisting of a vertical shaft at the ends of which transverse disks or rotulae are borne. There is always at least a trace of a subdermal cavity.

Many authors divide the Spongillidae into two subfamilies:--Spongillinae (or Euspongillinae), in which the gemmule-spicules have no transverse rotulae, and Meyeninae (or Ephydatiinae), 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 a.s.signed.

Minchin in his account of the Porifera in Lankester's "Treatise on Zoology" (1900) regards the Spongillidae merely as a subfamily of the Heterorrhaphidae, and there certainly are few differences of a definite nature between them and the marine family (or subfamily) Remeridae.

_Key to the Indian Genera of_ Spongillidae.

I. Microscleres without transverse disks.

A. Microscleres of the parenchyma similar in general structure to those or the gemmule; the latter without comb-like vertical rows of spines at the ends SPONGILLA, p. 67.

B. Microscleres of the gemmule with comb-like vertical rows of spines at both ends PECTISPONGILLA, p. 106.

II. Some or all of the microscleres birotulate.

(Birotulate microscleres of one kind only.) A. Microscleres of the gemmule birotulate, the rotules with serrated or strongly sinuous edges; parenchyma spicules usually absent, never of complicated structure EPHYDATIA, p. 108.

B. Microscleres of the gemmule as in _Ephydatia_; microscleres of the parenchyma consisting of numerous shafts meeting in different planes in a central nodule DOSILIA, p. 110.

C. Microscleres as in _Ephydatia_ except that the rotulae of the gemmule-spicules have smooth edges TROCHOSPONGILLA, p. 113.

D. Microscleres of the gemmule without a trace of rotules, those of the parenchyma birotulate CORVOSPONGILLA, nov., p. 122.

III. Microscleres of the gemmule with a well-developed basal rotule and a vertical shaft ending above in a mere k.n.o.b. TUBELLA, p. 120.

The most distinct genus of Spongillidae 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 a.s.signed by Weltner (Arch. Naturg. lxi (i) p. 131) to the subfamily Lubomirskinae are of doubtful position and need not be considered here; while _Lessepsia_, Keller, from one of the salt lakes on the Suez Ca.n.a.l, certainly does not belong to the family, although it is a.s.signed to it by von Lendenfeld (Mon. h.o.r.n.y Sponges, p.

904 (1889)) and subsequently by Minchin (Porifera, p. 152, in Lankester's Treatise on Zoology, part ii (1900)).

Genus 1. SPONGILLA, _Lamarck_ (Carter _emend._).

_Spongilla_, Lamarck, Histoire des Animaux sans Vertebres, ii, p. 111 (1836).

_Spongilla_, Carter, Ann. Nat. Hist. (5) vii, p. 86 (1881).

_Euspongilla_, Vejdovsky, Abh. Bohm. Ges. xii, p. 15 (1883).

_Spongilla_, Potts, P. Ac. Philad. 1887, p. 182.

TYPE, _Spongilla lacustris_, auctorum.

Spongillidae 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 Spongillidae, 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 Jura.s.sic (p. 52).

GEOGRAPHICAL DISTRIBUTION.--Cosmopolitan. In most countries the majority of the freshwater sponges belong to this genus, but in j.a.pan _Ephydatia_ seems to predominate.

_Key to the Indian Species of_ Spongilla.

I. Gemmule provided with a thick, apparently granular pneumatic coat in which the gemmule-spicules are arranged tangentially or vertically. (Subgenus _Euspongilla_, p. 69.) A. No foraminal tubule.

_a._ Sponge bright green, soft and compressiblewhen fresh, very fragile dry _lacustris_, p. 69.

_a'._ Sponge white or grey, hard both fresh and dry _alba_, p. 76.

B. A foraminal tubule present.

_b._ Skeleton-spicules smooth.

beta. Gemmules free; gemmule-spicules arranged tangentially and horizontally _proliferens_, p. 72.

beta'. Gemmules free; gemmule-spicules arranged vertically or nearly so in a single series _hemephydatia_, p. 82.

beta". Gemmules firmly fixed to the support of the sponge; gemmule-spicules almost vertical, irregularly arranged, as a rule in more than one series _travancorica_, p. 81.

_b'._ Skeleton-spicules spiny or irregular in outline.

beta"'. Gemmule-spicules tangential and horizontal, without rudimentary rotules _cinerea_, p. 79.

beta"". Gemmule-spicules vertical or nearly so, often with rudimentary rotules at the tips _crateriformis_, p. 83.