STUDIES IN ARTIFICIAL PARTHENOGENESIS. l6l 



moved with a pipette and dropped into Syracuse dishes filled 

 with 2 M MgCl 2 . Just two minutes after insemination, a 

 necessarily hasty examination of the eggs in the beaker showed 

 that all the eggs had well-elevated membranes at this time. 

 On the other hand, eggs removed from the beaker at the same 

 time and placed in 2 M MgCU, upon later examination, showed 

 no signs of ajt elevated membrane, and the membrane had 

 evidently been pushed back against the egg. In the following 

 table, the fractions in the second column indicate the proportion 

 of eggs which showed the membrane elevated in the various 

 Syracuse dishes. In each case, the numerator denotes the 

 number of eggs with membranes elevated, the denominator 

 the total number of eggs counted. 



Minutes after Insemination Membranes Elevated 

 Before Transfer to 2 M MgCk. (Free from Egg). 



1 0/50 



2 0/50 



3 1/50 



4 30/50 



5 49/50 



In the case of the eggs transferred to the MgClo solution 

 three minutes after insemination, some of the membranes were 

 not completely collapsed, but one, two, or even several small 

 globular expansions could be detected at the egg surface. 



This experiment was repeated on August 22, 1913, with almost 

 identical results. In this case the eggs were transferred to 

 2 M MgClo at intervals of 2, 3, 4 minutes after insemination. 

 At i^ minutes after insemination hasty observation showed all 

 the eggs to have well-elevated membranes. Thus the eggs 

 were placed in the magnesium chloride solution after membrane 

 elevation had occurred. Nevertheless, as the following table 

 shows, the eggs removed to MgCl2 two and three minutes after 

 insemination, showed no membranes free from the egg. 



After 2 minutes, 0/50 with membranes free from egg. 



3 i/50 



4 13/50 



These experiments were also confirmed in the summer of 

 1914. I have interpreted the results as indicating that after 

 elevation the membrane still remains impermeable to MgClo 



