PROLONGATION OF THE LIFE OF THE EGG 93 
while the cytoplasm of the unfertilized egg is surrounded by a 
chorion and by the cortical layer, which protect it. Hence the 
surface layer of the fertilized egg is more rapidly injured than 
that of the unfertilized egg, and this may account for the more 
rapid escape of pigment from the former. 
The fact that KCN or lack of oxygen prolongs the life of 
the egg in abnormal solutions might be interpreted as indicat- 
ing that the KCN prevents the diffusion of abnormal solutions 
into the egg. Wasteneys and the writer investigated this possi- 
bility in the fertilized eggs of purpuratus which were stained 
red with neutral red. Such eggs are rapidly destroyed in a 
mixture of NaCl+ KCl to which some N/10 NH,OH is added; 
while the addition of KCN prolongs their life in such a solution. 
This action was not caused by a retardation of the diffusion of 
NH,OH into the egg through the presence of KCN, for it was 
found that the eggs were just as quickly stained yellow in the 
solutions of NH,OH containing KCN as in those free from it. 
The life-saving action of KCN is therefore not due to any effect 
upon the permeability of the egg. 
All the facts agree with the assumption that the egg is more 
sensitive to abnormal solutions when its rate of oxidations is 
high or when certain developmental changes, e.g., cell divisions, 
take place than when it is at rest. 
There is, however, an apparent exception to the rule that 
the fertilized egg is more easily injured than the unfertilized; 
weak bases like NH,OH or the amines injure unfertilized eggs 
more rapidly than fertilized eggs. When we put unfertilized 
eges of Arbacia for twenty minutes at 23° C. into a mixture of 
50 e.c. m/2 NaCl+KCl+CaCl,+0.3 ¢.c. N/10 NH,OH and 
then transfer them to sea-water, they will begin to segment 
but will disintegrate very rapidly. If we put newly fertilized 
eggs for twenty minutes into the same solution we find that 
the short stay in the ammonia solution does not hurt them. In 
this experiment the injury to the unfertilized eggs is only the 
