22 NORTH AMERICAN FEVER TICK AND OTHER SPECIES. 
In a series of experiments with alternate cold and normal tempera- 
tures the eggs were kept in a refrigerator exposed to a mean tem- 
perature of about 45° F. from 8.30 p. m. to 8.30 a. m. During the 
day the eggs were removed from the refrigerator and remained at 
the temperature of the air. _ After six consecutive nights of exposure 
in this way from 5 to 10 per cent of the eggs hatched. It is probable 
that the necessary manipulation in these .experiments interfered 
with the viability of the eggs and that normally a considerably greater 
percentage would hatch under the same conditions. 
SUBMERGENCE OF EGGS IN WATER. 
Sixteen different lots of eggs were used to determine the effect of 
submergence in water. One-half were submerged for from 10 to 24 
days, and most of the eggs hatched. In another lot submerged 
for 25 days 33 per cent hatched. The experiments were _per- 
formed from June to September and the incubation period under 
water was not appreciably different from the normal at the different 
periods at which submergence took place. In all these experiments 
complete submergence was secured by means of a screen obstruc- 
tion below the surface of the water. Our results agree with those 
recently published by Messrs. Newell and Dougherty and with unpub- 
lished data obtained by Prof. H. A. Morgan, who suggested our 
experiments. 
The practical importance of these experiments is to show that the 
flooding of pastures would have no effect whatever on the viability 
of tick eggs on the ground. Not only would the great majority 
hatch, but the time of hatching would not be materially different 
from that in case no water whatever were present. As a matter of 
fact the flooding under some conditions, as, for instance, during a 
drought, might hasten incubation. 
These data, taken in connection with data mentioned elsewhere, 
showing the remarkable resistance of seed ticks to water, indicate 
clearly the reason why pastures overflowed for considerable periods 
have repeatedly been found to furnish tick infestation. 
A series of eggs varying from those recently deposited to others 
about to hatch were submerged in tube-form vials. To keep the 
eggs submerged absorbent cotton was pressed down into the water. 
None of the eggs hatched, and we suppose this was due to insuffi- 
cient aeration. 
Several lots of eggs that were kept in pill boxes until they had 
become thoroughly dried were placed on water in Stenter dishes to 
determine if hatching would follow. After submergence for a short 
period the eggs in large part filled out and appeared viable, but did 
not hatch. | 
