ore HELEN DEAN KING 
very great. One could not exclude the possibility, therefore, that 
selective mortality was responsible for the results, even if there 
is no evidence that mortality is ever selective in amphibian tad- 
poles reared under artificial conditions. 
In making the experiments mentioned above it was found that 
solutions of salt and of sugar as strong as 24 per cent could not be 
used on the unfertilized eggs for more than five minutes without 
rendering the great majority of them incapable of being fertilized. 
In continuing these experiments very weak solutions were em- 
ployed so that the mortality at the time of fertilization might 
be decreased. 
A batch of about 400 eggs, taken from female a, was placed in 
a 2 per cent solution of cane sugar; another batch of approxi- 
mately the same number of eggs was put in a 2 per cent solution 
of NaCl. Each lot of eggs remained in the solution for ten min- 
utes, and was then quickly washed off in running water and fer- 
tilized in tap water. At least 95 per cent of the eggs that had 
been subjected to the action of the salt solution segmented nor- 
mally. Comparatively few of the tadpoles died during the early 
stages of development, and the entire number of individuals in 
which sex was not ascertained was only 12 per cent. The results 
obtained with the eggs that had been placed in the sugar solution 
were even more satisfactory. Not more than 2 per cent of the 
eggs failed to develop, and only 7 per cent of the 300 individuals 
that were taken for rearing died before it was possible to ascer- 
tain their sex. In each of these lots, as shown in table 1, a per- 
centage of females was obtained that was considerably higher than 
that found among the toads that served as control for the exper- 
iments in this series. The latter individuals were developed from 
eggs of female a which had been fertilized in tap water with sperm 
from the same male that was used in the fertilization of all of the 
other eggs taken from this female. 
Eggs, taken from female 6, were subjected to the action of a 
2 per cent solution of sugar for twenty minutes and were then 
fertilized in tap water; only about 5 per cent of these eggs failed 
to segment. In 53, or 22.40 per cent, of the 250 tadpoles that 
were taken for development, the sex was not ascertained. This 
