STUDIES IN ARTIFICIAL PARTHENOGENESIS. 187 



farther, one reached a few-celled blastula stage. The control 

 of unfertilized eggs in sea-water showed practically no seg- 

 mentation, a count showed three out of more than five thousand. 



In the above experiment only about 30-40 per cent, of the 

 eggs underwent membrane elevation. In other experiments, 

 in which less concentrated solutions of KCN were employed, 

 all cortical change was inhibited and the eggs did not segment, 

 although nuclear division sometimes occurred. In order to 

 obtain the best results, widely elevated membranes must be 

 obtained. If the membranes were only lifted a short distance 

 from the egg in the cyanide-containing hypertonic sea-water, 

 on a return to normal sea-water the egg expanded until it again 

 came into contact with the membrane (often it ruptured the 

 membrane and an exovate was produced). The best results 

 were obtained in an experiment of September 2, 1914. In this 

 case, I c.c. of 1/5 per cent. KCN was added to 24.5 c.c. of sea- 

 water containing eggs, at 11:45 A.M. At 11:45 !/6 A. M., 

 4 c.c. of 2.5 M NaCl were added, so that the eggs were then in 

 "NaCl hypertonic sea-water" plus KCN. They were allowed 

 to remain in this solution for 33 minutes, during which time 

 it was noticed that ninety-seven per cent, underwent membrane 

 elevation. At 12:18 P.M., some eggs in 4 c.c. of the solution 

 were transferred to about 600 c.c. of sea-water in a tall graduate. 

 At about 12:45 P. M., most of the sea-water was siphoned off 

 from the graduate and fresh sea-water added. At 2:30 P.M., 

 out of 233 eggs examined 22 were found to have segmented, but 

 the count was evidently too low, as doubtful cases were rejected. 

 In some instances, exovates simulated cleavage. Only those 

 eggs in which a nucleus could be observed in each cell were 

 counted. At 4:55 P.M., 50 eggs, out of 110 examined, were 

 found to have segmented, but this count was likewise probably 

 too low. At 9 P.M., hundreds of motile blastulae could be 

 observed. (Of 337 eggs noted, 28 were motile larvae, of these 

 18 swam on the bottom, 10 on the top.) 



These experiments indicate that the action of the hypertonic 

 solutions in initiating development is not due to an effect on 

 the oxidative processes, for the hypertonic solution has the same 

 action in the presence of a concentration of KCN, which ac- 



