ACTIVATION OF THE EGG BY BASES 151 



been in 50 c.c. m/2 (NaCl+KCl+OjiCl 2 )+0.3 c.c. N/10 

 NaOH for forty-two minutes remained practically intact and 

 the same was true for the eggs that had been in the tetraethyl- 

 ammoniumhydroxide for forty-two minutes. In order to make 

 sure that they did not only appear normal but were normal, 

 sperm was added to these eggs the next morning. All those 

 that had been in NaOH, and in tetraethylammoniumhydroxide, 

 segmented normally and developed into normal embryos. 



In this experiment part of the eggs were submitted for fifteen 

 minutes to the action of the neutral hypertonic solution after 

 they had been treated with alkali. Those that had been in 

 NH 4 OH developed into larvae, the others did not. It is 

 obvious that the changes leading to parthenogenetic develop- 

 ment are brought about more rapidly by NH 4 OH than by the 

 strong bases. 



5. We have seen in the experiments with the fertilization 

 of the eggs by fatty acid that the treatment with the hyper- 

 tonic solution could either precede or follow the treatment with 

 fatty acid. In case it preceded, the exposure to the hypertonic 

 solution had to be considerably longer than when it followed the 

 fatty acid treatment. The same is true for the fertilization 

 by bases. If the eggs of purpuratus are submitted to the hyper- 

 tonic solution first, they must remain much longer in the hyper- 

 tonic solution than if they are put into it after having undergone 

 a treatment with alkali. This is clue to the difference in the rate 

 of oxidations in the egg before and after membrane formation. 

 When the rate of oxidation is higher in the egg the exposure to 

 the hypertonic solution may be shorter. 



It may be stated incidentally that artificial parthenogenesis 

 by bases is less satisfactory in S. purpuratus than in Arbacia 

 since only the eggs of perhaps one-third of the females of 

 purpuratus develop into larvae through the influence of bases. 

 Where the method is successful it can be shown that NH 4 OH, 

 and to some degree the amines, are more effective tluin NaOH. 



