of the Freshwater Sponges in the Tanks of Bombay. 307 



length is about one quarter of the diameter of the body, and ap- 

 parently corrugated like the neck of the entozoon Cysticircus 

 longicollis. These transparent little sacs (the gemmules of Grant 

 and Hogg ?) are sometimes filled with green matter. They ap- 

 pear to be able to adapt themselves to any form that may be 

 convenient for them to assume, and when forcibly separated from 

 each other (by tearing to pieces a minute portion of the sponge 

 under water in a watch-glass), the isolated individuals may be 

 seen to approach each other, and to apply themselves together 

 in twos and threes, &c., and so on, until, from a particle only 

 discernible by the microscope, they assume the form of an aggre- 

 gate visible to the naked eye, and such a portion, growing and 

 multiplying, might ultimately reach the size of the largest masses 

 adhering to the sides of the tanks at Bombay. They appear to 

 belong to the genus Amoeba of Ehrenberg. Dujardin has re- 

 cognized them, and they are correctly figured (as they appear 

 under a lens of one-tenth of an inch focus) in Johnston's ' British 

 Sponges,' p. 61 ; — as well as certain filaments, which the day 

 after a piece of sponge has been treated in the way which I have 

 just mentioned, may be seen extended from them, terminating 

 or not in little transparent bulbs ; floating, or fixed by their ex- 

 tremities, branching irregularly, long or short, each branch ter- 

 minating or not in a bulb, and presenting similar pedicellated 

 bulbs here and there in its course ; when fixed on the watch- 

 glass, disposed irregularly in straight lines intersecting each 

 other, — radiating from a common centre or bulb, or in the form 

 of an areolar membrane ; frequently moniliform, as if they grew 

 by the addition of cells to their free extremities. 



The aggregated position of the animals I have described, im- 

 bedded in the transparent tissue of the sponge, bears a great re- 

 semblance to that of some of the Compound Tunicated Animals ; 

 especially in their ultimate development into a mass, intersected 

 in all directions by canals, to allow of the presence of that ele- 

 ment which is necessary for their existence, — the freedom they 

 possess in the early part of their life, of moving through the 

 water or creeping over the surfaces of solid bodies, and their 

 ultimate destination of becoming permanently fixed in a granulo- 

 gelatinous mass, secreted or formed by themselves. 



There is also a curious fact connected with the vitality of the 

 Freshwater Sponges, and I think it also prevails with the Sea 

 Sponges, for it was by observing the latter and their seed-like 

 bodies, in the amorphous species, that I was first led to notice it. 

 It is, that they may be taken out of their natural element, dried, 

 and kept for months, without losing their vitality. This I have 

 inferred from observing the sponges attached to the rocks on the 

 upper parts of the tanks, which are uncovered for many months 



