Improved Method op artificial Parthenogenesis B9 



Hence membrane formation is essential for development, and 

 it is immaterial how the membrane formation has been pro- 

 duced; except that the membrane formation induced by a 

 fatty acid injures the egg less than that provoked by most of 

 the other substances. 



4. In the experiments thus far discussed the treatment with 

 the hypertonic solution preceded the artificial membrane forma- 

 tion with the fatty acid. Fertilization with sperm, however, 

 begins with membrane formation; and hence it was natural to 

 find out, whether in artificial parthenogenesis also, membrane 

 formation by means of a fatty acid might not be appUed as the 

 first step. 



The unfertilized eggs were therefore subjected to treatment 

 with a fatty acid until they all formed membranes. Ten to 

 twenty minutes later they were placed in hypertonic sea-water. 

 It turned out that in this order of events the eggs of S. purpur- 

 atus need remain in the hypertonic solution only a relatively 

 short time, some thirty to sixty minutes at about 15° C 

 The development of the eggs is nearly identical with that evoked 

 by sperm, and practically all the eggs develop; provided that 

 the details of the method are correctly carried out. 



The procedure for the chemical activation of the unferti- 

 Hzed egg of (S. purpuratus is therefore as follows. The eggs 

 are placed in 50 c.c. of sea-water 4-2. 8 c.c. of N/10 butyric acid 

 (which must be thoroughly mixed beforehand). At 15° C. 

 a portion of the eggs is transferred after one and one-half, 

 two and one-half, and three or four minutes to 200 c.c. of sea- 

 water which had previously been made ready for this purpose. 

 In one or all of the dishes all the eggs form a normal fertilization 

 membrane. 



It may be observed, by the way, that too many eggs must not 

 be put into the acid sea-water, since otherwise the mass of acid 



1 The eggs of Arbacia need remain in the hypertonic solution only about 20 

 minute.s at a temperature of 22° C. 



