612 STUDIES IN GENERAL PHYSIOLOGY 
from those that had been treated with the stronger MgCl, 
solution, however, was the fact that the former all had regular 
and sharp outlines and were free from débris. The outlines 
of the blastule were much more spherical. These blastule 
had greater vitality than the others and kept alive during the 
next thirty-six hours. 
The next morning a 
number of them had 
(co) reached the pluteus 
LS =‘ stage with a perfectly 
normal skeleton and 
intestine, but they 
died the following day 
f) (Fig. 151). They had 
YS? lived more than two 
Oh days. Their develop- 
ment was slower than 
in the case of fertil- 
ized eggs. 
All these blastulee 
and plutei swam about on the bottom of the dish, not rising 
to the surface like the larvee from fertilized eggs. 
The control eggs that had been left in the normal sea- 
water remained unsegmented, with the exception of a few 
which on the second day were found divided into 2 or 3 cells. 
The latter, of course, segmented no further. None of these 
eggs had a membrane. 
Seventh series.—The preceding series had shown that a 
mixture of equal parts of 2,on MgCl, and sea-water is more 
favorable for the development of the eggs than a mixture 
with more MgCl, and less sea-water, for instance 60 e.c. 
MgCl, and 40 c.c. sea-water. In the latter mixture the eggs 
seemed to suffer more. It must, however, be stated that as 
far as the comparative number of eggs is concerned that 
FIG, 151 
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