Spongilla, Lamarck, Histoire des Animaux sans Vertèbres, ii, p. 111 (1836). Spongilla, Carter, Ann. Nat. Hist. (5) vii, p. 86 (1881). Euspongilla, Vejdovsky, Abh. Böhm. Ges. xii, p. 15 (1883). Spongilla, Potts, P. Ac. Philad. 1887, p. 182.
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.
| I. | Gemmule provided with athick, apparently granular pneumatic coat in which the gemmule-spiculesare arranged tangentially or vertically. (Subgenus Euspongilla,p. [69].) | |
| A. | No foraminaltubule. | |
| a. Spongebright green, soft and compressible when fresh, very fragile dry | lacustris, p. [69]. | |
| a'. Sponge white or grey, hardboth fresh and dry | alba, p. [76]. | |
| B. | A foraminal tubulepresent. | |
| b.Skeleton-spicules smooth. | ||
| β. Gemmulesfree; gemmule-spicules arranged tangentially and horizontally | proliferens, p. [72]. | |
| β'.Gemmules free; gemmule-spicules arranged vertically or nearly so in asingle series | hemephydatia, p. [82]. | |
| β''.Gemmules firmly fixed to the support of the sponge; gemmule-spiculesalmost vertical, irregularly arranged, as a rule in more than oneseries | travancorica, p. [81]. | |
| b'. Skeleton-spicules spiny orirregular in outline. | ||
| β'''.Gemmule-spicules tangential and horizontal, without rudimentaryrotules | cinerea, p. [79]. | |
| β''''.Gemmule-spicules vertical or nearly so, often with rudimentary rotulesat the tips | crateriformis, p. [83]. | |
| II. | Gemmules surrounded inseveral layers by distinct polygonal air-spaces with chitinous walls.(Subgenus Eunapius, p. [86].) | |
| A. | Gemmules single.Skeleton- and gemmule-spicules smooth, pointed, not very stout | carteri, p. [87]. |
| B. | Gemmules boundtogether in pairs. Skeleton friable; skeleton-spicules slender | gemina, nov., p. [97]. |
| C. | Gemmules boundtogether in free groups of more than two or forming a "pavement-layer"at the base of the sponge. | |
| c. Skeleton friable;skeleton-spicules slender | fragilis,p. [95]. | |
| c'. Skeleton very hard andresistant; skeleton-spicules stout | crassissima, p. [98]. | |
| III. | Gemmules without orwith irregular pneumatic coat, covered by a chitinous membrane ormembranes in which the gemmule-spicules lie parallel to the surface.(Subgenus Stratospongilla, p. [100].) | |
| A. | Skeleton spiculesspiny or irregular in outline. | |
| a. Skeleton-spicules blunt;gemmules covered by a single chitinous membrane | indica, p. [100]. | |
| a'. Skeleton-spicules sharp;gemmules covered by two chitinous membranes | bombayensis, p. [102]. | |
| B. | Skeleton-spiculessmooth. Skeleton-spicules sharp; gemmule spicules very irregular inform | ultima, p. [104]. |
Subgenus A. EUSPONGILLA, Vejdovsky.