E. E. Atkin and A. Bacot 
495 
effective, the watery extract was far less so, and in one tube had no 
effect at all within three-quarters of an hour. The difference in the 
results in the several tubes must be taken as measure of the variable 
susceptibility of the eggs. It will be noted that in one of the tubes to 
which the living yeast cells were added, there was only a partial response 
within the first three-quarters of an hour. It is regrettable that no 
tubes containing eggs which had long lain dormant were available to 
control results, as was done with the previous trial (Experiment XXIV). 
In discussing these results it is necessary to note that hatching may 
follow if during the sterilizing process the eggs are left too long in lysol. 
Sometimes these eggs do not uncap until after their transference to 
water, but in both cases the larvae fail to come right out of the shell. 
The same phenomena followed when eggs were exposed to formalin 
vapour for several hours. After transference to water large numbers 
uncapped, but the larvae only partially came out of the shells. In 
these instances no movement on the part of the larvae was ever 
observed. It is possible that they were killed within the egg, but cut 
or partially cut the cap in their dying struggles. There is a difficulty 
in the way of the acceptance of this explanation, however, because it 
is not easy to understand why, in the case of those placed in lysol, the 
uncapping should sometimes be delayed until after they were trans¬ 
ferred to water. 
The differential hatching of the eggs may, as pointed out in the intro¬ 
ductory notes, arise as an hereditary trait owing to an adaptation to 
meet the needs of seasonal changes. On the other hand there is evidence 
that treatment during incubation or prior to full immersion may be the 
cause of more ready response to immersion. Bacot (1916) found when 
in Freetown that of a given batch of eggs, which had incubated on a 
wet surface, 98 % of those which were immersed without allowing them 
to dry hatched within 30 minutes; of a portion of the same batch 
placed in water after 24 hours’ drying the hatching of 84 % was dis¬ 
tributed over a period of 65 days; while the balance of the batch, 
which was kept dry for 7 days before immersion, again showed a 
divergent result, 43 % hatching within 24 hours, another 11 % follow¬ 
ing within 51 days and of the balance 8 % containing living larvae 
when dissected after 81 days. 
In Experiment XVI the eggs were not allowed to dry before 
sterilization, as it was desired to test the theory that a check in the 
influence of bacterial action on the eggs might be the cause of delay 
in their hatching when subsequently immersed. Although the larvae 
