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 KCl 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.24 n KCl 
+ 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 KCl 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 KCl solution. 
If they remain too long in such a solution, the KCl 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 KCl that must be added to 
sea-water in order to bring about artificial parthenogenesis 
of the Chetopterus eggs. The following solutions were used: 
(1) $cc. 242 KCl +99} c.c. sea-water 
(2) 1 . “ +99 “ 
@) «+984 . 
(4) Normal sea-water (control) 
The eggs were left in these solutions over night. The 
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