Errect oF ArtiriciAL 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 
4+1c.c. ofa 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, 60, 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 KCN 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 
[ took up these experiments afresh. In order to convince 
