No. 3.] BUDDING IN PEROPHORA. 397 
to this observer, cells wander out from the ectoderm, fasten 
themselves to the ventral wall of the dorsal tube, and there 
form the ganglion. These wandering ectodermal cells were 
also observed by Pizon, who described them as giving rise to a 
portion of the genital gland, to muscular fibers, and to certain 
cells of the blood. The principal difference, then, between the 
three authors is that, whereas Pizon and Oka hold to an inde- 
pendent origin of hypophysis and ganglion, Hjort maintains 
that there is a common rudiment for the two structures. 
The results of Salensky (27) on the bud development of 
Distaplia do not stand in the slightest agreement with any 
of those obtained for Botryllus. The nervous system of the 
Distaplia bud is of ectodermal origin, according to him. Cells 
sink down at a very early period from the ectodermal wall and 
form a solid mass, which later acquires a cavity, increases in 
length, and produces a tube. The latter becomes differentiated 
into three parts; the anterior gives rise to the hypophysis, the 
middle to the ganglion, and the posterior portion to the visceral 
nerve. The hypophysis and ganglion have, therefore, a common 
origin. This mode of formation, however, is only true of the 
primordial bud; for all the other buds, which are produced from 
it by fission, derive their nervous system by division directly 
from that of the parent along with the rest of their organs. 
It might be mentioned that in the buds of Pyrosoma, 
Salensky (26) has described a similar ectodermal origin of the 
nervous system, although Seeliger (30) in the same form derives 
the common rudiment of ganglion and hypophysis from meso- 
dermal cells. 
Salensky’s results on Distaplia are directly contradicted by 
Hjort and Frl. Bonnevie (10). The latter find no trace of the 
nervous system in the early stage at which Salensky describes 
its first appearance, but maintain, on the contrary, that a 
forwardly directed diverticulum is later formed from the dorsal 
wall of the inner vesicle, just as in Botryllus, and that the 
ganglion is differentiated from the wall of the dorsal tube. 
Pizon (22), in his work on Botryllus, states that he has made 
observations on the development of the dorsal tube in the buds 
of a number of other ascidians. In Perophora and Clavelina he 
