Effect of Artificial Membrane Formation 79 



in the sea-water poor in oxygen, some (about 1 per cent) devel- 

 oped to perfectly normal plutei after they were transferred to 

 normal sea-water. Experiments with potassium cyanide gave 

 the same results. Unfertilized eggs in which a butyric acid 

 membrane had been formed were placed in 50 c.c. of sea-water 

 -f-l c.c. of a 1 per cent KCN solution. Here the concentration 

 was forty times as large as is necessary for the inhibition of 

 the division of the fertilized egg and for the prevention of 

 the disintegration process. Some of the eggs were trans- 

 ferred to normal sea-water after 18, 30, 45, 65, and 85 

 minutes. Of the eggs placed in normal sea-water after 45 

 and 65 minutes a small number, about 5 per cent, developed. 

 In this case, however, the development did not start till fourteen 

 hours after the eggs were taken out of the sea-water that con- 

 tained the potassium cyanide. I suppose that several hours 

 are necessary for all the hydrocyanic acid to disappear from 

 the egg. This conjecture is supported by the fact that only 

 those eggs developed which were placed after treatment with 

 potassium cyanide in flat watch glasses in which they were 

 covered only by a shallow layer of water, and in which therefore 

 the evaporation of the HCN could proceed quickly. The 

 development of the eggs was also favored by passing a stream 

 of oxygen through the watch glasses for a minute. But similar 

 results could also be obtained with smaller quantities of KCN. 

 Thus, in one experiment, the eggs were placed after artificial 

 membrane formation in 50 c.c. of sea-water to which 1, 2, 4, 

 and 8 c.c. of 1/10 of 1 per cent KCN had been added. They 

 remained in these solutions for from one to twenty-three hours. 

 A few of the eggs which had been transferred from the solutions 

 with 2 and 4 c.c. of 1/10 of 1 per cent KGN to normal sea-water 

 after from three to seven hours developed into larvae. 



It struck me in these experiments that the development of 

 the eggs appeared wonderfully normal, and so several years ago 

 I took up these experiments afresh. In order to convince 



