30 



IVIorpliology of Cordylophora : — a, hyclrosoma of Cordylo- 

 jphora lacustris, grooving on a dead ralve of the swan-mussel ; b, 

 longitudinal section of a portion of its ecenosarc, with a single 

 polypite ; c, another fragment of the same ccenosare, to which 

 are attached, a polj-pite, and three reproductive bodies, or gono- 

 phores, in various stages of development, the largest and most 

 advanced containing ova ; — o, mouth ; 5', cavity behind the 

 mouth ; 5, gastric cavity ; k', interior of the ccenosare ; ev, endo- 

 derm ; /it, muscular layer; «k, ectoderm; €«', outer hard layer, 

 or polypary, excreted by ectoderm ; €/c", processes of ectoderm, 

 connecting it with the inner surface of this hard layer. (All, ex- 

 cept a, magnified.) 



