88 Mr. H. J. Carter on the Freshwater Sponges of Bombay. 



cells, possessing also a like but more limited power of motion. 

 [I do not however wish it to be inferred from this close resem- 

 blance, that I am of opinion that the seed-like body is but an 

 aggregate of separately developed sponge-cells ; on the contrary, 

 there are always present among the cells of a piece of sponge 

 which has been torn to pieces, many which contain within them 

 (developing from their upper an inner surface) a number of 

 transparent cells of various sizes, not unlike the hyaline vesicles 

 in appearance, but all adhering together in a mass. It may 

 perhaps be one of these cell-bearing cells which becomes the 

 seed-like body. They are distinguished from the common sponge- 

 cell by the character I have mentioned, by their containing fewer 

 granules, and by their greater transparency, but in every other 

 respect they are exactly like the sponge-cell.] To resume how- 

 ever the subject of the development of the seed-like body, — it 

 passes from the state just mentioned into a more circumscribed 

 form, then becomes surrounded by a soft, white, compressible 

 capsule, and finally thickens, turns yellow, and developes upon 

 its exterior a firm crust of siliceous spicula. 



Thus matured, its cells (Plate III. fig. 6 b), which were ori- 

 ginally unequal in size, have now nearly all become equal, almost 

 motionless, and a little exceed the average diameter of the largest 

 sponge-cells ; while their germs (Plate III. fig. 6 a), which in the 

 first instance so nearly resembled the granules of the sponge- 

 cells, are now four or five times larger, and vary in diameter be- 

 low the 3 oV o* n P ar ^ °f an mcn > which is the average linear mea- 

 surement of the largest of their kind. 



The capsule (Plate III. fig. 6/) has now passed from its soft, 

 white state into a tough yellow coriaceous membrane, presenting 

 in Meyeni and plumosa a hexagonally tessellated appearance 

 (fig. 6 c), on the divisions of which rest the asteroid disks (fig. Qe) 

 of the vertically-placed spicula (fig. 6 g) which surround it. 



In the two species just mentioned the spicula are arranged 

 perpendicularly to the surface of the capsule, and the interval 

 between them is filled up with a white siliceous, amorphous matter, 

 which keeps them in position. Each spiculum extends a little 

 beyond this matter, and supports on its free end a toothed disk, 

 similar to the one on its fixed end which rests on the capsule ; so 

 that the external surface of the seed-like body in Meyeni and 

 plumosa is studded with little stellated bodies; while in the other 

 species, where there appears to be no such regular arrangement 

 of these spicula, a number of smooth or spiniferous points is 

 presented. 



Development of Spongilla. — When the cells of the seed-like 

 body are forcibly expelled from their natural cavity, under water, 

 they are irregular in form and motionless, but soon swell out (by 



