POLYZOA 187 



Most species of the Entoprocta are dioecious, and the 

 generative organs have special ducts. Besides the sexual 

 reproduction, they multiply also by the formation of buds. 

 This process amongst the Polyzoa is remarkable, inasmuch 

 as the endoderm is not represented in the tissues of the bud ; 

 in most other animals which reproduce by budding, all the 

 three embryonic layers occur in the bud. 



The affinities of the Polyzoa are somewhat obscure. The 

 developement of the Entoprocta and their adult structures 

 point to the origin of the group from some ancestor which 

 is represented in the ontogeny of the MoUusca, Chaetopoda, 

 and armed Gephyrea by the Trochosphere larva. On the 

 other hand, the Phylactolaemata have a certain marked resem- 

 blance to the unarmed Gephyrea, and if this resemblance 

 be not homoplastic, we must regard the Gymnolaemata, and 

 still more the Entoprocta, as degenerate forms. 



