612 



STUDIES IN GENERAL PHYSIOLOGY 



from those that had been treated with the stronger MgCl 2 

 solution, however, was the fact that the former all had regular 

 and sharp outlines and were free from debris. The outlines 

 of the blastulse were much more spherical. These blastulse 

 had greater vitality than the others and kept alive during the 



next thirty-six hours. 

 The next morning a 

 number of them had 

 reached the pluteus 

 stage with a perfectly 

 normal skeleton and 

 intestine, but they 

 died the following day 

 (Fig. 151). They had 



lived more than two 

 $\ 



days. Their develop- 

 ment was slower than 

 in the case of fertil- 

 ized eggs. 



All these blastulse 

 and plutei swam about on the bottom of the dish, not rising 

 to the surface like the larvae 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 -$n MgCl 3 and sea- water is more 

 favorable for the development of the eggs than a mixture 

 with more MgCl 3 and less sea- water, for instance 60 c.c. 

 MgCl 2 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 



