No.1.] BUDDING IN GOODSITRIA AND PEROPHORA. E75 
urspriinglichen Knospe ; aber da die betreffende Stelle gerade 
im Winkel zwischen der mittleren Blase und der Anlage des 
linkern Peribranchialsackes liegt, ist es schwer zu entscheiden, 
ob sie speciell der ersteren oder der letzteren entstammt.”’ 
Hjort also (93), p. 602, found the pericardium of the Botry/- 
fus bud to appear first as a solid cell mass ; but concerning 
the origin of this mass, whether from the “endoderm” or 
from mesoderm cells he was not able to decide. 
Pizon ('93), p. 44, on the other hand, describes it as arising 
in this genus as a small diverticulum, and neither from the 
branchial nor the peribranchial sacs, but from the primitive 
vesicle. 
But whether it begins as a solid cell mass or as a diverticu- 
lum signifies very little ; and of almost as little significance is 
the question whether it arises from the primitive vesicle, from 
the branchial sac, or from the peribranchial sac, since its point 
of origin is at this stage of development an indifferent point as 
regards the three structures mentioned. It is not at all impos- 
sible that absolute exactness in observation would find it to 
arise from the branchial sac in some individuals, from the 
peribranchial sac in others, and from the primitive vesicle in 
others. Indeed, the observed facts in relation to variations 
in the time and position of appearance of different organs 
make such a conjecture rather probable. 
The only fundamental question raised is as to the possibility 
of a mesodérmal instead of an endodermal origin, This 
question, and also the question of the epicardium, I shall 
discuss after having presented my observations on the devel- 
opment of the organ in Pevophora. The formation of the 
heart by an invagination of the pericardial vesicle is here 
so entirely similar to what is well known in many other 
Ascidians that a detailed description of the process would be 
superfluous. A mere reference to Figs. 29 and 30, Pl. XIV, 
in which two stages in the development are incidentally shown, 
will suffice. 
