No.1.] BUDDING IN GOODSIRIA AND PEROPHORA. 165 
This does not seem to be the case. At any rate, as we shall 
presently see, at a still more advanced stage, z.e. after the bud 
has become fully severed, the wall of the inner vesicle is, in 
some buds at least, still entirely undifferentiated. 
Fig. 15, Pl. XIII, shows a section of a bud that is very nearly 
severed from its parent; in fact, the severance is practically 
complete, there being a mere neck of scattered cells, v.c., mark- 
ing the former connection between bud and parent. It is here 
seen that the ectoderm of the zooid is not fully closed together 
at the point where the bud was cut away. Here the inner 
vesicle is wholly undifferentiated, it presenting in every section 
the same appearance as that shown in the one figured ; and it 
should be said that buds occur in which every trace of the 
connecting strand has disappeared, but in which the inner 
vesicle still retains its simple, unmodified condition. However, 
it does not appear to remain long in this state. 
In describing the further growth of the bud it will be best 
to follow the course of development of each organ separately, 
but before beginning the description I wish to call attention to 
the interesting fact that 2” different buds the order of appear- 
ance and stages in development of the several organs are subject 
to considerable variation with reference to one another. I will 
point out specific instances of this as I proceed with the 
description. 
5. DEVELOPMENT OF THE ORGANS. 
a. The Branchial and Peribranchial Sacs. 
I have been unable to make my observations on entire buds 
and on sections agree exactly regarding the initial step in 
the formation of these structures. By examining whole buds 
the impression is gained that the process is begun by the 
growth of two folds which will ultimately form partitions 
separating the primitive simple vesicle into three portions — two 
lateral ones, the peribranchial sacs, and a middle one, the 
branchial sac. “These folds are seen:at pf, Fig: 17, Pl. XIII, 
in which their formation is already advanced to a considerable 
extent; but in Tig. 16 the slight angles marked by the same 
