173 



On the Statoblasts of the Freshwater Sponges. 



By B. W. Priest. 



(Read November 24th, 1882.) 



PLATE VII. 



Having lately been engaged in examining the Statoblasts of the 

 species of Freslnvater Sponges at present known, and being struck 

 with their marvellous structure and beauty, I thought a few words 

 about them might interest some of the members of the Quekett 

 Club, although I know the two British species have been ably 

 treated by Mr. Waller. 



I shall not enter into the general structure of the different species 

 now known, but confine myself to the Statoblasts of the typical 

 specimens' of each genus, noting any particular deviation of form 

 that may occur as we proceed, and mentioning any j:>eculiarity in 

 the form of those Sponges in which the Statoblasts are unknown. 



The Freshwater Sponges were first made known as far back as 

 1696, and in 1745 Linnseus described two species under the re- 

 spective names of Spongia Jiuviatilis and Spongia lacustris, mention- 

 ing at the same time the presence of the small seed-like bodies 

 generally associated with them. 



These organisms have been named by different writers on the 

 subject at various times, gemmules, ovules, ovisacs, spherules, cap- 

 sules, and lastly statoblasts or winter eggs, from their close 

 resemblance to the statoblasts of the Freshwater Bryozoa, not only 

 in outward ajupearance but also in their being, according to Mr. 

 Carter, similar in general internal structure, the difference being only 

 in size and form, in having spicules instead of tentacular appen- 

 dages on their surface, and in the mode of discharging their contents 

 when matured. 



Now, as there have never been any forms found in the Marine 

 Sponges at all resembling the Statoblasts found in the Freshwater 

 Sponges, a sharp line of demarcation between the two is here indi- 

 cated by that circumstance alone. 



