Synascidia of the (9^enua Col ella. 135 



probably remain for a very long and variable time before 

 evolution takes place. In the development all the organs are 

 formed at the expense of the internal cells, the ectoderm 

 charged with reserve material being a simple envelope, of 

 which the thickness diminishes gradually. 



It would be very interesting to study minutely the organo- 

 genesis in these buds 6, and to compare it with that of the 

 buds a. I have not been able to carry it out so fully as I 

 desired, the presence of the vitellus rendering it difficult to 

 prepare sections of material already stale and not preserved 

 in the special manner required for histological investigation. 

 Nevertheless, from the facts observed I can conclude with all 

 but perfect certainty that the organogenesis is the same in 

 the two cases. Further, there exist between the extreme 

 types of bud transitional forms in which the reserve material 

 is more or less abundant. 



This example of the polymorphism of buds appears to me 

 to be very interesting for the following reasons : — 



1. It is the property of a special form of Corni ; I have 

 not observed it in tlie species in which the peduncle is not 

 sharply separated from the part which contains the adult 

 ascidiozooids. The buds loaded with reserve material ai-e 

 those which, by their position, do not develop immediately. 

 It appears that they can pass through their various stages by 

 themselves ; now it is probable that they regenerate the 

 colony when the head is amputated, and it would be very 

 curious to produce wounds upon these forms in the living 

 state* — to destroy the head, for example, and study the 

 subsequent behaviour of the peduncle. I would also recall 

 the fact that this tendency is analogous to others presented 

 by certain compound Ascidians at the time of hibernation. 



2. Tliese facts seem to me to be specially important in the 

 general history of budding in the Ascidians. The external 

 wall of the bud arises always from the ectoderm of the parent, 

 and the internal vesicle is in general of endodermic origin. 

 A study of the blastogenesis shows, howevei*, that it is this 

 internal vesicle which furnishes all the organs of the blasto- 

 zooid, even those, such as the peribranchial cavity and the 

 nervous system, which, in the oozooid, were ectodermic. The 

 external vesicle is reduced to the role of integument. Here 

 we see it charged with reserve material — a remarkable fact, 

 seeing that in general the reserves localize themselves in the 

 endodermic and mesodermic tissues. But this new function 



* Unfortunately, so far as at present known, they are confined to the 

 seas south of the Equator. 



