68 BULLETIN OF THE 
which any bud arises goes to form that bud; but some of it is, appar- 
ently, passed along under the highly metamorphosed cells of the ecto- 
derm, again to divide itself, one part going to form a new polypide, the 
other to form the Anlagen of new buds. In Cristatella, this embryonic 
mass of cells of the inner layer of the bud seems to be to a considerable 
extent independent of the highly metamorphosed ectoderm, and to form 
at places a sort of third layer, lying below the true ectoderm and above 
the muscularis with the coelomic epithelium. Here, too, while it is 
easy to see buds arise from preceding buds in the adult colony, we 
cannot consider our question answered until we have discovered the 
origin of the cells from which, as from a stolon, the Anlagen of polypides 
successively arise. 
I desire to say that I have avoided giving a full account of the on- 
togeny of these species, both because it is not directly required for the 
solution of the problems in hand, and because we are promised studies 
in this field by Braem. 
The eggs of Phylactolamata arise, as has long been affirmed, from the 
cœlomic epithelium of the body wall. The evidence of this is conclusive, 
for one often gees in a single section various stages in the development 
of the eggs. (Plate XI. Fig. 93, ov.) It is also to be observed that 
they do not arise indiscriminately from any region of the body wall, but 
always close to the neck of a polypide. Sooner or later these eggs, 
surrounded it may be by a few follicular cells, are enclosed in an oœcium, 
and here undergo their development up to the stage of a young stock, 
possessing perhaps a dozen immature polypides. In the figures on 
Plates XI. and XII. the oweium (o«@.) has been usually drawn, but in 
Figures 100 and 104 it has been omitted. As a result of cleavage, a 
blastula is formed, and from one pole of this — the pole nearest to the 
neck of the ocecium — cells are given off which move into the blastocoel 
(Figs. 94, 98) and finally come to line the cavity. It is important to 
observe that in the earliest stage of this process found there were four 
inner cells, of which two are represented in the section (Fig. 94, ms drm. 
+ewdrm.). Thus the two layers of the adult body wall are established. 
Up to this stage the conditions are practically the same in Cristatella 
and Plumatella. From now on, they are somewhat different in the two 
genera, 
The first difference to be noticed is in the oweium itself. In Crista- 
tella the cells composing this rapidly become a pavement epithelium 
(Fig, 97); in Plumatella, on the contrary, the cells of the ocecium 
remain columnar (Fig. 99). The neck of the oweium also differs in the 
