548 ALFEED C. H ADDON. 



have observed it iii this position in the young cell of Beania 

 mirabilis; and in this species Joliet has convinced himself 

 that the uolypide is actually derived from the endosarcal cord. 

 In the rudimentary zooecium of Victorella pavida the 

 foiming polypide seems to me [Hincks] to be enveloped in the 

 endosarcal plexus, and to be (in all probability) produced by 

 it, . . . It may be, as Joliet suggests, that the authors 

 who have referred it to the endocyst have not been sufficiently 

 alive to the distinction between these two tissues. It may be 

 that the function is to some extent shared by the endocyst " 

 (Hincks, pp. 1, li). 



Joliet thus clearly believes in the endosarcal origin of the 

 bud. This 'endosarc' is, by him, derived from the endocyst. 

 In his use of the term 'endocyst' one must not understand 

 both layers, but only the outer. This seems to be clear from 

 Joliet's account, and from his deriving migratory cells also 

 from the growing end of the outer layer. The inner layer of 

 the endocyst (peripheral mesoblast or somatopleure) is com- 

 posed, according to all authors, of fusiform cells — i. e. cells 

 similar to the characteristic cells of Joliet's endosarc. It is 

 thus certain that Joliet would consider the buds of the Polyzoa 

 as composed solely of mesoblastic tissue, or possibly of some 

 modified epiblast as well. 



We have seen that in Flustra carbasea the tentacles and 

 the mouth area arise from one mass of tissue, and from the 

 latter an invagination takes place forming the mouth and 

 oesophagus (Stomodaeum) ; whereas the stomach and intestine 

 ari^e from another mass of tissue. These two closed sacs 

 (Stomodscum and stomach) later on unite to form a continuous 

 tube. It was this well marked double origin of the digestive 

 tract which first led me, when in Naples, in I8T9, to study 

 the question of Polyzoan gemmation. I have already enume- 

 rated some of the forms in which I have since seen the same 

 phenomenon. 



The resemblance of the above to the formation of similar 

 structures in the embryos of so many animals is most striking, 

 and seems to suggest that we have here to deal with an epi- 



