Mr. H. J. Carter on the Freshwater Sponges of Bombay. 87 



The granules are round or ovoid, translucent, and of an eme- 

 rald or yellowish green colour, varying in diameter below the 

 T2 <io o^h P ar ^ °f an mcn ; which is the average linear measurement 

 of the largest. In some cells they are so minute and colourless 

 as to appear only under the form of a nebular mass, while in 

 others they are of the largest kind and few in number. 



The hyaline vesicles on the other hand are transparent, colour- 

 less and globular, and although variable in point of size like the 

 green granules, are seldom recognized before they much exceed 

 the latter in diameter. They generally possess the remarkable 

 property of slowly dilating and suddenly contracting themselves, 

 and present in their interior, molecules of extreme minuteness in 

 rapid commotion. 



When living and isolated the sponge-cell is polymorphous, its 

 transparent or non-granular portion undergoing the greatest 

 amount of transformation, while its semi-transparent or granular 

 part, which is uppermost, is only slightly attracted to this side 

 or that, according to the point of the cell which is in the act of 

 being transformed. 



The intercellular substance, which forms the bond of union 

 between the cells, is mucilaginous. When observed in the deli- 

 cate pellicle, which, with its imbedded cells and granules, it forms 

 over the surface and throughout the canals of the sponge, it is 

 transparent ; but when a portion of this pellicle is cut from its 

 attachments, it collapses and becomes semi-opake. In this state 

 the detached portion immediately evinces a tendency to assume 

 a spheroidal form; but whether the intercellular substance partici- 

 pates in this act, or remains passive while it is wholly performed 

 by the habit of the cells which are imbedded in it, to approximate 

 themselves, I have not been able to determine. 



Seed-like Bodies. — The seed-like bodies occupy the oldest or 

 first-formed portions of the sponge, never its periphery. They 

 are round or ovoid according to the species, and each presents a 

 single infundibular depression on its surface which communicates 

 with the interior. At the earliest period of development in which 

 I have recognized the seed-like body, it has been composed of a 

 number of cells united together in a globular or ovoid mass (ac- 

 cording to the species) by an intercellular substance similar to 

 that just described. In this state, apparently without any cap- 

 sule, and about half the size of the full- developed seed-like body, 

 it seems to lie free, in a cavity formed by a condensation of the 

 common structure of the sponge immediately surrounding it. 

 The cells of which it is now composed appear to differ only from 

 those of the full-developed sponge-cell in being smaller, in the 

 colourless state of their germs, and in the absence of hyaline 

 vesicles ; in all other respects they closely resemble the sponge- 



