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 
ageregate 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 imer surface) a number of 
transparent cells of various sizes, not unlike the hyaline vesicles 
in appearance, but all adhermg 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-lke 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 ILI. fig. 6 6), 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 =j5,th part of an inch, which is the average linear mea- 
surement of the largest of their kind. 
The capsule (Plate III. fig. 6f) has now passed from its soft, 
white state into a tough yellow coriaceous membrane, presenting 
in Meyent and plumosa a hexagonally tessellated appearance 
(fig. 6c), on the divisions of which rest the asteroid disks (fig. 6e) 
of the vertically-placed spicula (fig. 6g) 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 Meyent 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 smocth or spiniferous points 1s 
presented. 
Development of Spongilla——When the cells of the seed-lke 
body are forcibly expelled from their natural cavity, under water, 
they are irregular in form and motionless, but soon swell out (by 
