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.
| I. | Microscleres withouttransverse disks. | |
| A. | Microscleres of theparenchyma similar in general structure to those or the gemmule; thelatter without comb-like vertical rows of spines at the ends | Spongilla, p. [67]. |
| B. | Microscleres of thegemmule with comb-like vertical rows of spines at both ends | Pectispongilla, p. [106]. |
| II. | Some or allof the microscleres birotulate. (Birotulate microscleres of one kindonly.) | |
| A. | Microscleres of thegemmule birotulate, the rotules with serrated or strongly sinuous edges;parenchyma spicules usually absent, never of complicatedstructure | Ephydatia,p. [108]. |
| B. | Microscleres of thegemmule as in Ephydatia; microscleres of the parenchymaconsisting of numerous shafts meeting in different planes in a centralnodule | Dosilia, p. [110]. |
| C. | Microscleres as inEphydatia except that the rotulæ of the gemmule-spicules havesmooth edges | Trochospongilla, p. [113]. |
| D. | Microscleres of thegemmule without a trace of rotules, those of the parenchymabirotulate | Corvospongilla, nov., p. [122]. |
| III. | Microscleres of thegemmule with a well-developed basal rotule and a vertical shaft endingabove in a mere knob. | Tubella, p. [120]. |
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)).
Genus 1. SPONGILLA, Lamarck (Carter emend.).