654 STUDIES IN GENERAL PHYSIOLOGY 
of a certain amount of water on the part of the egg caused 
the parthenogenetic development of the eggs of Cheetopterus 
in these experiments, it now remained to ascertain how long 
the eggs must remain in these solutions in order to develop. 
I put the unfertilized eggs of a female into a mixture of 
85 c.c. sea-water+20c.c. 24n NaCl. The first lot were taken 
out of this mixture after ten minutes, the second after thirty, 
the third after sixty, the fourth after ninety, and the fifth 
after one hundred and twenty minutes. The same evening 
(nine hours later) I found swimming trochophores among 
the eggs that had been taken out of the third and fourth 
lots. The eggs of the first lot did not show any trace of 
development at that time. Of those of the second lot about 
one in a hundred had begun to develop. In the fifth lot the 
eggs had apparently undergone development, but I found no 
swimming larve. The eggs had possibly been injured by 
their long stay in the more concentrated sea-water. 
The next morning about 20 to 40 per cent. of the eggs 
of the third and fourth lots were swimming about in the 
trochophore stage. The rest did not contain any living 
larvee, although some of the eggs were in the early segmen- 
tation stages. 
It is therefore necessary to leave the unfertilized eggs of 
Cheetopterus more than thirty and less than one hundred and 
twenty minutes in a mixture of 85 c.c. sea-water + 20 c.c. 2n 
NaCl in order to cause them to reach the trochophore stage. 
Conclusions.—From these experiments we are allowed to 
draw the following conclusions: 
1. The unfertilized eggs of Chetopterus do not reach the 
trochophore stage if left in normal sea-water, provided the 
proper precautions are taken against contamination by sper- 
matozoa. Such eggs show no change during the first seven 
to nine hours, but may begin to segment after that time. In 
such cases the segmentation as a rule does not proceed beyond 
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