THE FRESHWATER SPONGES. 170 



in Geodia and Pachymatisma, and termed by the late Dr. Bower- 

 bank Ovaria ? " My answer is that they are certainly not Ovaria. 



Dr. Bowerbank was evidently misled by the depressions which 

 are found to exist in these bodies. If we break up any of them, 

 as I have often done, from their earliest form of development, we 

 shall find that it is merely a depression and not an aperture leading 

 to an internal cavity, as no such cavity exists, and that the " glo- 

 bular crystalloids," as they are now termed, are consolidated 

 aggregations of spicules radiating from the centre to the circum- 

 ference, and forming one solid mass, being no more ovarian than 

 the stellate forms of spicules found in Tethya, or the silicious or 

 calcareous bodies found packed in the cells of some of the Tuni- 

 cated Ascidians. Dr. Bowerbank's statement of their being Ovaria 

 moreover is not borne out by the figures intended to illustrate 

 what he says. 



For further particulars, a paper by Mr. Carter in the " Annals 

 of Natural History," for July, 1869, containing remarks on the 

 same subject, may be consulted. 



Since writing this, Mr. Carter has kindly sent me a copy of 

 his paper in the " Annals of Natural History " for the present 

 month, describing a new species from Bombay — Spongilla bom- 

 bay emis ; and also calling attention to one shortly to be published 

 and described by Mr. Potts of Philadelphia, found at Chester 

 Creek — Spongilla segregata, the Statoblasts of which are developed 

 in a capsule, four together; the capsule being composed of hexa- 

 gonal cells, such as are found in S. Carteri and S. nitens ; the 

 whole reminding one of the appearance of the tetrahedral form of 

 the sporangium in certain plants. 



Perhaps I ought not to leave the subject without making some 

 statement as to the way the young Sponge is produced from the 

 Statoblast, but as I unfortunately have not seen the process myself 

 I may be allowed to quote Mr. Carter, our present great authority 

 on the subject, as briefly as I can : — 



" In due season the cellular contents are discharged through the 

 foramen into the water, and undergo a remarkable development 

 appearing as a white flocculent substance, having a flat, trans- 

 parent, irregular margin, containing numerous vesicles, whilst in 

 its central portion are ova-bearing or reproductive cells. At the 

 same time generally two kinds of spicula3 appear, which are formed 

 in the interior of special nucleated cells. They at first present 

 themselves as delicate lines, but rapidly grow by external additions 



