No. 3-] BUDDING IN PEROPHORA. 399 
annectens and P. listert. In both species he derives the com- 
mon rudiment of the hypophysis and ganglion from cells which 
wander out from the dorsal wall of the inner vesicle. 
After this short review of the state of our knowledge regard- 
ing this much confused subject, I shall now give an account of 
my own observations on the development of the dorsal tube and 
ganglion in the buds of Perophora viridis. 
My results, which are based on a study of an uninterrupted 
series of stages, have led me to believe that the conclusion 
which Seeliger drew from purely theoretical considerations 
concerning the origin of these structures in Clavelina is also 
true of Perophora viridis. I shall try to show that she dorsal 
tube and ganglion are derived from amoeboid cells of the 
blood. 
The dorsal tube is formed long before the ganglion, and the 
rudiment from which it will arise is first indicated just after the 
collection of cells which is to produce the pericardium makes 
its appearance. When the difference in thickness between the 
right side and the rest of the vesicle is becoming apparent — 
hence at a time when the rotation is about beginning — in the 
anterior portion of the bud, a little to the left of the median 
dorsal line, there is seen an irregular elongated patch of cells 
very loosely grouped together and lying on the outer surface 
on, inewinner. vesicle: (Pl) XXIG) Pies 13.) 2.2.72), ~ The tree 
amoeboid cells in the space between the ectoderm and endoderm 
are especially numerous in this region, and are closely associated 
with the collection of cells adhering to the vesicle. Although 
I have examined my sections with the greatest care under an 
oil-immersion lens, from the very first appearance of the rudi- 
ment, I have failed to find any indication of cell migration 
from the endodermal wall, and, therefore, cannot confirm 
Ritter’s statement (/.c., p. 368) that an “indistinguishable 
transition from the cells of the ‘endoderm’ to those of the 
neuro-hypophyseal anlage is to be traced,”’ and also that cells 
can be found “in the act of migrating from the ‘endoderm’ 
into the anlage.” 
The line of separation between the rudiment and the wall of 
the vesicle is seen to be perfectly distinct and clearly marked, 
