226 BUNTING. Vor 1x. 
shaken apart. Often the two separated blastomeres were 
found to be irregular in shape, but they each became spherical 
in a short time. In the blastomeres separated at the two- 
celled stage, the cleavage progressed as in the normal process, 
and with the same intervals, up to the eight-celled stage. 
(Figs. 37-42.) 
There were comparatively few of those shaken, or cut apart, 
which developed to the planular stage; but as the number was 
relatively small upon which the experiment was tried, and as 
there is a large percentage of death amongst the ova and 
embryos, even under normal conditions, it cannot be asserted 
with certainty that the separation has such a deleterious effect 
as to greatly increase the death rate. The planular stage is 
somewhat delayed, also the planulae much smaller in.size than 
the normal embryo. In Fig. 43, we have an elongated embryo 
of about eighteen hours, which is still opaque and unciliated, 
while the normal embryo is swimming at this time. In three 
days, we have a planula swimming very slowly, and rather 
peculiar in shape (Fig. 44). This had become pinkish in tint 
in about twenty-six hours, and it is possible that it may have 
moved sooner, although so sluggishly, that I had failed to 
observe the movement before this time. 
Although I have searched among the few sections I possess 
of these half embryos, to determine whether the endoderm arises 
through multipolar delamination, as in the normal embryo, 
I have been unfortunate in not being able to satisfactorily 
demonstrate this. That the endoderm is formed by delamina- 
tion is shown by Pl. III, Fig. 62, in which a karyokinetic 
figure is seen; this might indicate unipolar delamination, but 
we have every reason to believe that the origin of the endoderm 
follows the same general plan as in the normal embryo. 
Fig. 62 shows that the ectoderm cells then form into a row 
of columnar cells, with a sharply defined outline between them 
and the endoderm cells, and that the latter break down to form 
the central cavity. 
The four blastomeres were separated at the four-celled 
stage. These quarter embryos later became four-celled, but 
they were so small that I was unable to follow the segmenta- 
