SEX-DETERMINATION IN AMPHIBIANS a yal 
Altogether 4224 tadpoles were used in the various experiments, 
and of this number 3784 individuals were carried through to 
metamorphosis and their sex ascertained. The mortality in the 
entire series was, therefore, only 10.41 per cent, which is much 
less than the mortality that must occur in any lot of eggs laid 
under natural conditions. Whatever explanation may be offered 
for the unusual sex ratios obtained in some of these experiments 
it is evident that they cannot be ascribed to selective mortality. 
According to Davenport (’97), water forms from 60 per cent 
to 90 per cent of the whole mass of protoplasm in nearly all kinds 
‘of cells and is of the utmost importance for the various chemical 
processes taking place in the living organism. It is conceivable, 
therefore, that placing eggs under conditions that would alter 
their water content just before or during the time of fertilization 
might favor the development of one sex or the other, if it be that 
the sex of an individual depends upon some definite metabolic 
process occurring during the fertilization period. Some investi- 
gations made along this line last year gave such suggestive results 
that this past spring I confined my experiments with the eggs of 
Bufo to an attempt to ascertain whether the normal proportion 
of the sexes would be altered if the water content of the eggs was 
changed at or before fertilization. 
For convenience in description these experiments are divided 
into two classes: (1) those in which the water content of the 
unfertilized eggs was affected; (2) those in which the eggs were 
subjected to conditions that altered their water content during 
the fertilization period. 
1. EXPERIMENTS ON THE UNFERTILIZED EGG 
Former experiments in which unfertilized eggs of Bufo were sub- 
jected to the action of hypertonic solutions of salt and of sugar 
gave results which strongly suggested that the normal sex ratio 
had been altered by the treatment which the eggs had received 
previous to their fertilization (King, 711). Unfortunately the 
mortality at the time the eggs were fertilized, and also among 
the tadpoles during the early stages of their development, was 
