No.1.] BUDDING IN GOODSIRIA AND PEROPHORA. 207 
gl.ev., which I believe to be the evagination ; and there is also 
no doubt that the cells of the Az/age are continuous with those 
of the vesicle wall. While it is true that, as shown by the 
figure, the evagination is not clearly defined either as to its 
cellular wall or as to its cavity, I am unable to see any valid 
objection against regarding it as such; the chief difficulty, so 
far as I see, lies in the fact that the instance is an isolated one. 
It is impossible that such a condition can be general, since, as 
already said, I have seen it in a single bud only among the 
large number examined of practically the same developmental 
stage. It may be asked if we have not here a rather late stage 
of development in which the mouth of the hypophysis is already 
formed ; and if the opening here figured does not represent it. 
But when the entire series of sections is examined and com- 
pared with those from younger and older buds, there is really 
no ground for question on this point. The hypophysis mouth 
is not formed till a considerably later time, and it is always a 
well-defined opening, but smaller than this. It is my strong 
belief that originally the ganglio-hypophyseal Anlage arose from 
the inner vesicle by an evagination in Perophora, just as it does 
in Goodstria, Botryllus, Glossophorum, and Distaplia. For 
some unaccountable reason the process has undergone second- 
ary modification, till in most cases, in P. annectens at least, the 
evagination has been wholly replaced by a cell proliferation. 
Occasionally, however, the earlier evaginate process is reverted 
to; and such a case is presented in the individual shown in 
Fig. 74. The individual variation here seems to be somewhat 
similar to that which occurs in the gastrulation of Aurela 
flavidula, where it has been recently shown, Miss Hyde (94), 
that in some instances the endoderm is formed by a regular 
invagination, while in others it is formed, in part at least, by 
delamination and by inwandering of the blastosphere cells. 
The completion of the hypophyseal duct and the differentia- 
tion of the ganglion from its dorsal wall takes place relatively 
later here than in Goodsiria. It will be remembered that in 
the latter species the duct is well formed, and the ganglion 
entirely separated from it at a stage when the peribranchial 
sacs are but just begun and the endostyle is still scarcely 
