662 STUDIES IN GENERAL PHYSIOLOGY 



Lot 5 (thirteen minutes) had trochophores which did not 

 yet move, and in lot 6 (twenty minutes) and lot 7 (forty 

 minutes) trochophores were found that were just beginning 

 to move. The control eggs were absolutely unsegmented. 



The next morning I found no trochophores in the first 

 lot (one minute), but many eggs in a two- to eight-cell stage. 

 In lot 2 (three minutes) about 1 per cent, of the eggs were 

 swimming about as trochophores. In lot 4 about 10 per 

 cent, of all the eggs were swimming about as trochophores ; in 

 lot 5 (13 minutes) it was about the same. In lot 6, whose 

 eggs had been for twenty minutes in the KC1 sea-water, 

 about 50 per cent, swam about in the trochophore stage. 

 Lot 7 seemed to contain not quite so many trochophores. 



It is therefore necessary that the unfertilized eggs re- 

 main more than one minute in a mixture of 2 c.c. 2^ n KC1 

 -f- 98 c.c. sea- water in order to develop; three minutes (or 

 possibly a little less) is sufficient. This indicates clearly 

 that a certain quantity of K or KC1 must enter the egg in 

 order to bring about the development. This quantity is 

 very small. It seems to vary, however, for the individual 

 eggs, inasmuch as the number of eggs that developed was 

 greater the longer the eggs remained in the KC1 solution. 

 If they remain too long in such a solution, the KC1 acts like 

 a poison. From twenty to sixty minutes seems to be the 

 optimal time. 



Seventeenth series. I wished to determine once more 

 what was the smallest amount of KC1 that must be added to 

 sea-water in order to bring about artificial parthenogenesis 

 of the ChaBtopterus eggs. The following solutions were used: 



(1) Jc.e. 2Jn KC1 + 99J c.c. sea-water 



(2) 1 " " +99 " 



(3) 1} " +98J 



(4) Normal sea -water (control) 



The eggs were left in these solutions over night. The 



