INITIATION OF DEVELOPMENT IN CH^ETOPTERUS. 29 



germinal vesicle, the migration of its contents to the animal pole, 

 and the formation of an apparently normal spindle, but not to 

 normal membrane relations. The n/2 calcium chloride and n/2 

 magnesium chloride led to the break-down of the germinal vesicle, 

 but the migration of the contents of the vesicle to the animal 

 pole did not follow. In the n/2 magnesium chloride the mem- 

 brane relations were fairly normal, but not so in the n/2 calcium 

 chloride. 



Combinations of the salts \tere made according to the following 

 Van't Hoff formula: 



n 



NaCl 10 c.c. 

 2 



n 

 KC1 0.22 c.c. 



2 



n 



- MgCl 2 1.2 c.c. 



n 



- CaCl-2 0.2 c.c. 



2 



When 10 c.c. of n/2 NaCl was used with 1.2 c.c. of n/2 MgCl 2 (no 

 KC1 or CaCl 2 being present), the results were normal in all par- 

 ticulars. Evidently then, potassium chloride and calcium chlo- 

 ride are unnecessary to the first developmental stage. When, 

 however, 0.22 c.c. of n/2 KC1 or 0.2 c.c. of n/2 CaCl 2 were substi- 

 tuted for n/2 MgClo with n/2 NaCl, the spindles formed as normally 

 but the membrane relations were not normal. Magnesium chlo- 

 ride seems to have some definite effect in inducing normal mem- 

 branes, therefore, ano*either n/2 sodium chloride or n/2 potassium 

 chloride may induce normal spindles. Salt solutions are not neces- 

 sary to induce certain of the developmental changes, however, as 

 is seen by experiments with neutral paraffin oil and with cane 

 sugar. 



D. Neutral Paraffin Oil. When the ovaries were opened in this 

 liquid a certain number of eggs, although not all by any means, 

 appeared to behave normally in that the vesicle contents migrated 

 to the animal pole, and the maturation spindle formed, but the 

 eggs swelled slightly and the membrane did not stand off from 



