EFFECT OF ARTIFICIAL MEMBRANE FORMATION 81 



minutes after membrane formation behaved in a similar manner. 

 Others, transferred eighty-two minutes after membrane forma- 

 tion, gave few larvae. 



These experiments were repeated quite often, but the results 

 were not always equally good. It is possible that the eggs of 

 various females did not react equally well to this method. 



In the more recent experiments the eggs were first washed 

 two or three times with ordinary sea-water after being taken 

 from that containing potassium cyanide. 



In all these experiments the perfect regularity of the seg- 

 mentation was very striking; the segmentation is almost as 

 good as in eggs fertilized with sperm. This is an important fact, 

 in view of the experiments in which the disintegration of the 

 eggs after membrane formation is prevented by hypertonic 

 sea-water. In this case the first division is often somewhat 

 irregular. The experiments with potassium cyanide show 

 that this irregularity is essentially a secondary effect of the 

 hypertonic salt solution, and that membrane formation alone 

 leads to a normal segmentation. 



Secondly it must be remarked that in these experiments the 

 larvae stayed on the surface of the sea-water as in normal devel- 

 opment, and gave large numbers of plutei. The shorter the 

 time that the eggs had remained in the potassium cyanide 

 solution, the larger the number of eggs that developed into 

 normal plutei. The reason is obvious. Membrane formation 

 sets going (or accelerates) the chemical reactions which deter- 

 mine development. If we interrupt the oxidations in such an 

 egg, there will accumulate in it decomposition products which 

 ought to be removed by oxidation. I suppose that this accu- 

 mulation of decomposition products leads to the injury of the 

 egg, which is shown by the fact that the longer the eggs remain 

 in the cyanide solution, the more their vitality is impaired. 

 We have had the same experience with sea-urchin eggs ferti- 

 lized with sperm, which also lose their vitality more quickly 



