Xll INTRODUCTION. 



of conical cells placed closely together, their basal surfaces 

 turned towards the ectocyst and forming an irregular 

 mosaic work, whilst their opposite pole is directed towards 

 the centre. These cells possess a distinct nucleus, and 

 are very refractive. 



Amongst the JLctoprocta {Pedicellina, &c.) the endo- 

 cyst consists of a layer of polygonal cells, with strongly 

 refractive oval nuclei, which lies close upon the inner 

 surface of the ectocyst. In this division its cellular 

 character is distinguishable at all points, though it is 

 more clearly and strongly marked towards the upper 

 extremity of the peduncle ^. 



As to the specific functions of the endocyst, it has 

 been held that it gives origin directly to all buds formed 

 within the coencecium, and to the generative products of 

 both kinds f. According to this view, it is the source 

 of the polypide, and of both the ovary and spermary. 

 A different role, however, has been assigned to it by 

 the able French biologist Joliet ; and it will be neces- 

 sary to consider somewhat in detail the very important 

 conclusions to which his researches have led him. It 

 will be more convenient, however, to do this hereafter ; 

 and I shall merely state generally at present that he 

 regards the endocyst as specially charged with the en- 

 largement of the colony, and also as giving origin to a 

 distinct tissue, which he names (provisionally) the endo- 

 sai'c, to which are really assignable the functions hitherto 

 credited to the endocyst, and others beside. 



Connected with the endocyst is an apparatus of 



* Joliet, op. cit. p. 61. 



t Nitscbe, " Ueb. die'Morphologie d. Bryozoeii," Zeitsch. 1". wiss. Zool. 

 xxi. Heft 4, p. 102. 



