ARTIFICIAL PARTHENOGENESIS 581 



eggs segmented, and only after a long search was it possible to find 

 a swimming larva on the following day. 



These experiments, which were repeated a number of times, indi- 

 cate that the weak base NHiOH is rnuch more efficient in the causa- 

 tion of artificial parthenogenesis than the strong bases NaOH, KOH, 

 and tetraaethylammoniumhydr oxide. 



If.. Action of alkalies alone, without the action of hypertonic 



solution 



0.3 cc. ^ NH4OH, 0.3 cc. ^ NaOH, and 0.3 cc. ^ tetra- 

 aethylammoniumhydroxide were added to 50 cc. m/2 (NaCl 

 + KCl + CaCL) respectively. Unfertilized eggs of Arbacia 

 were put into these three solutions for forty-two minutes and 

 then transferred to normal sea water. All of the eggs that had 

 been in the solution containing the NH4OH segmented in a 

 rather amoeboid way into two or four cells, after which the 

 cells fell part and disintegrated. All of the eggs that had been 

 in 50 cc. m/2 (NaCl + KCl + CaCls) + 0.3 cc. ^ NaOH for 

 forty-two minutes remained practically intact and the same 

 was true for the eggs that had been in the tetraaethylammoni- 

 umhydroxide 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 the eggs that 

 had been in NaOH, and in tetraeathylammoniumhydroxide, 

 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. The eggs that had been 

 in NH4OH developed into larvae, the others did not. It is 

 obvious that the changes leading to parthenogenetic develop- 

 ment are brought about considerably more rapidly by NH4OH 

 than by the strong bases. 



All this is in complete analogy with the action of acids in 

 artificial parthenogenesis. Only the acid or alkali which enters 

 the egg can act, and since NH4OH enters much more rapidly 

 than the strong bases, the weak base NH4OH is more efficient 

 than the strong bases. 



