No. 3.] BUDDING IN PEROPHORA. 385 
I think doubtful, their direct origin from the inner vesicle has 
been completely lost, as they do not appear until quite a late 
stage, and then merely as prolongations backward of the lateral 
portions of the peribranchial cavity, after the latter have been 
entirely cut off from the inner vesicle. This would, therefore, 
be a still more modified condition than that which is found in 
Botryllus. 
Pizon (oc. ct¢., p. 105) makes the statement, which is not, 
however, illustrated by figures, that he has confirmed on the 
buds of Perophora listeri the results of Kowalewsky (13, Ama- 
roucitum proliferum) and of Van Beneden and Julin (33, Clave- 
lina rissoana) in regard to the origin of the epicardial tube. 
«Ce tube,” he says, “ résulte bien de la reunion de deux petits 
diverticules qui naissent a droite et a gauche du sac branchial 
et qui s isolent complétement de celui-ci 4a un moment donné.” 
Such a description is not in the slightest accord with my 
observations, and if an epicardial tube arises in this manner in 
the buds of the European Perophora, it certainly does not in 
Perophora viridis. 
The Branchial Sac or Pharynx. 
That portion of the original inner vesicle which is left after 
the separation of the peribranchial cavity becomes the pharynx. 
At its anterior end it finally opens to the exterior through the 
branchial orifice, and after the appearance of the gill slits com- 
municates with the peribranchial cavity, while posteriorly it 
leads off into the digestive tract. 
The formation of the branchial sac in the buds of Perophora 
viridis is complicated by reason of the peculiar shifting of the 
inner vesicle, which has been described above. The whole 
vesicle, with the exception of the anterior end, which, as already 
stated, is but slightly involved in the process, becomes shifted 
or revolved through about 90°, in such a way that the original 
right wall of the vesicle comes to lie ultimately on the ventral 
side. This right wall, as has been shown, is early found to be 
much thicker than the rest of the vesicle, the difference being 
due, not to an increase in thickness of this region, but to the 
