608 



STUDIES IN GENERAL PHYSIOLOGY 



poisonous effect of the Mg ions, and it seemed possible to me 

 that a decrease in the amount of MgCl 2 and a slight increase 

 in the amount of sea-water might allow the eggs to reach 

 the pluteus stage. The eggs of two females were distributed 

 in the following solution: 



(1) 60 c.c. \-n MgCl 2 +40 c.c. sea-water 

 (2)50c.c. " +50 

 (3) Normal sea -water 



The eggs were brought back into normal sea-water after 

 one hour and five minutes, one hour and thirty minutes, and 



1:55 



2.04 



2:07 



2:09 



z-.is. 



FIG. 148 



one hour and forty minutes. Only the eggs of the last lot 

 that had been in the solution one hour and forty minutes 

 showed the beginning of a development. I believe that I 

 took out the eggs too soon. In some cases such eggs are 

 able to develop, but in others they are not, and I think it 

 probable that if the eggs had been left a little longer in so- 

 lution 1 or 2 they would have developed further. I made 

 some camera drawings of the way in which the eggs were 

 segmented (Fig. 148). The successive stages of the segmen- 

 tation of one and the same egg up to the .six-cell stage 

 were drawn. The reader will see from the drawings that the 

 egg went within twenty minutes from practically an undivided 



