374 Mr. Hogg's Observatloyis on the Spongilla fluviatilis, 



Now the opinion which first struck me was the actual identity of these two 

 bodies ; that is to say, tliat the latter are only a younger and less mature 

 condition of the former bodies ; and this indeed appeared to me not impro- 

 bable, considering that (although the same mass of Sponge possesses at the 

 same period both sorts) they both in certain of their stages mutually approach 

 very near in appearance and size to each other ; for I have noticed in the 

 same fresh specimen the least seedlike bodies to be of a white colour with 

 their envelopes soft and destitute of any apparent orifice at their tops. 



Again, the largest germlike bodies which I have seen were more globular 

 in their shape, without any terminal orifice, having the enveloping mem- 

 branes, except a very small portion at their upper extremities, no longer 

 transparent, by reason of the quantity of the opake matter having so much 

 increased within them : tiie colour also of some that I preserved in spirits 

 had lost its original whiteness, and changed to a yellowish brown or buff, the 

 most usual colour of the full-grown seedlike bodies. Hence my grounds for 

 supposing that the germlike bodies are only early forms of the seedlike bodies, 

 which they would ultimately become when either sufficiently matured or at 

 their proper season of the year*. 



To this, however, there is one objection, namely, the absence of all papillae 

 in the one, and the presence of them in the other : yet I think it not un- 

 likely that the seedlike bodies once possessed those organs ; for on being 

 highly magnified, their outer shells appear indented with small dots, which 

 make me rather imagine that they are the spots where the papillae may have 

 originally been attached, but which, on the maturity of those bodies, either 

 all or part decayed or enlarged into fibres, whereby they are fastenedf within 



intermixed with very small granules (most probably the young locomotive germlike bodies), which also 

 seem to contain a particle of the same jelly, that will increase with the growth of the granules, after 

 they may have escaped from the former body. Now I think, from my own observations, it is clear 

 that this jelly is alone the reproductive or vital portion from which the substance of the sponge itself 

 originates. 



* Of course many of these would never ripen into seedlike bodies ; \\z. those which have emerged 

 from the pores and canals of the parent structure, and having swum to a convenient spot, there begin 

 to grow. These form an exception to the above supposition, which can only apply to such numerous 

 germlike bodies as cannot escape from the fibrous network of the Sponge. 



t Some of the fixed seedlike bodies frequently become detached by the decay of their connecting 

 fibres or tubules ; by the burrowing and tearing of insects, and other parasitical animals ; or by the 



