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 Chsetopterus 

 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 -f 20 c.c. 2-|n NaCl. The tirst 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 larvae. 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 

 larvaB, although some of the eggs were in the early segmen- 

 tation stages. 



It is therefore necessary to leave the unfertilized eggs of 

 Chffitopterus more than thirty and less than one hundred and 

 twenty minutes in a mixture of 85 c.c. sea-water + 20 c.c. 2^)i 

 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 Qhsetopterus 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 



