100 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



formation. If eggs fertilized with sperm are placed in 50 c.c. 

 of sea-water, to which increasing amounts of 2J m NaCl are 

 added, it can be seen that the addition of 1 c.c. of 2J m NaCl 

 to 50 c.c. of sea-water has no effect on the development; the 

 addition of 2 c.c. of 2J m NaCl retards the first division, but to a 

 scarcely noticeable degree; while the addition of 3 c.c. increases 



TABLE VIII 



NATURE OF THE SOLUTION 



PERCENTAGE OF EGGS THAT DEVELOPED INTO LARVAE 

 AFTER REMAINING IN THE SOLUTION 



the time of the first division by about 12 per cent of its usual 

 length, although the development of the eggs proceeds almost 

 normally. The addition of 4 c.c. of 2J m NaCl to 50 c.c. of 

 sea-water is the first to delay the first cleavage for several hours 

 (over 100 per cent of the normal length) ; it is true that the eggs 

 can develop very slowly in this solution, but not all the eggs are 

 able to develop. Hence it appears that here too the addition 

 of 4 c.c. of NaCl is of critical importance. In 50 c.c. of sea- 

 water -j- 5 c.c. 2| m NaCl the eggs do not develop beyond the 

 thirty-two- to sixty-four-cell stage. Probably, therefore, in a 



