134 ^r. Maurice Caullery on (he 



persistent at least during a certain number of bla^togenetic 

 generations, as I have already noticed in Distaplia magni- 

 larva. 



(3) The facts observed lead me to consider the origin of 

 the buds as identical with that described by Kovalewsky, 

 Delia Valle, and Salensky in Distaplia. I have seen nothing 

 which can allow one to admit a budding at the expense of the 

 inferior ectodermic prolongation of individuals, as Herdmann 

 believed to be the case. 



But I wish to insist especially upon a curious peculiarity 

 of the buds in a group of species. They are those in which 

 the Corm is composed of a more or less globular head, 

 borne upon a long peduncle, in such a way that the whole 

 reminds one somewhat of a mushroom. 



On studying the peduncle it is seen that at the periphery 

 the cell-structure of the tunic is compact and resistant, whilst 

 in the central region it is composed of large vesicular cells, 

 80 common in other Tunicata. It is this central region which 

 contains the buds, often packed in great numbers and pressed 

 one against the other. It would appear that, when the evolu- 

 tion of a generation is ended, the globular terminal portion of 

 the Corm where it occurs may be cut off, and that the 

 peduncle regenerates a new head by the development of the 

 buds which it contains. An examination of the buds in 

 different portions of the same Corm reveals the following 

 facts : — 



(«) In the immediate neighbourhood of the head of the 

 Corm buds are to be found in every stage of development, 

 recalling very much by their structure those of Distaplia and 

 containing no reserve matei-ial. The external vesicle of these 

 buds is formed by an epithelium, which is very fiat and thin. 

 The oldest of these buds penetrate into the head of the 

 Corm. 



{h) On the contrary, in the parts of the peduncle distant 

 from the head of the Corm the buds, at the beginning of 

 their development, have the appearance externally of eggs 

 rich in vitellus. On studying them one observes that at the 

 centre a group of cells, deprived of reserve material, is to be 

 found, corresponding with the internal vesicle and the mesenchy- 

 matous cells of the buds a, and that all the reserve material, 

 the appearance and reaction of which are those of vitellus, is 

 accumulated in the cells of the external vesicle. The relations 

 of size of the central mass and of the ectodermic layer so 

 modified are often those of the germinative vesicle and the 

 entire egg in a compound Ascidian at the moment when the 

 germinative vesicle is most developed. These buds very 



