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IOWA ACADEMY OF SCIENCE Voi.. XXVIII, 1921 
weather (November) ; the other (796 fish) in warm weather 
(March). In the appended table I have presented data concern- 
ing these shipments, from which the following may be seen : 
(1) . The Gambusia in both shipments show a high general 
death-rate. 
(2) . At both seasons, the death-rate for males was greater 
than that for females. 
(3) . In the cold- weather shipment, the male death-rate was 
approximately times the female death-rate; in the warm- wea- 
ther shipment, approximately 2^ times the female death-rate. 
(4) . The death-rate for females in the March shipment was 
only 11/6 times that of the November shipment. 
(5) . The death-rate for males in the March shipment was 
practically double that of the November shipment. 
From the foregoing it is evident that the male is more suscep- 
tible to injuries incidental to shipment than the female, and that 
temperature is not the main factor involved in the high general 
death-rate. 
This latter conclusion is further supported by the results of a 
series of experiments in which Gambusia were, by ten-minute 
stages, brought into water of increasing temperature. The fish 
apparently suffered no discomfort when the water in their con- 
tainer was thus, in forty minutes, raised through 20° C and neither 
sex showed any marked or peculiar behavior. Therefore, as a 
result of these experiments, I am convinced that the cause of 
the high general mortality-rate in shipments of Gambusia is due, 
rather, to injury in catching, and to crowding in the container, 
than to warming, more or less rapid, of the water. In the cau- 
sation of the higher death-rate of the males, injury of the intro- 
mittent organ may also have a part. 
The conclusion of Barney and Anson, regarding the supposed 
higher death-rate of females, rests, in my opinion, on very slen- 
der support. They say in part : 
It might he thought that the higher temperatures produced a 
high mortality rate in males. This is not the case, however, for 
in September of each year there is a decided increase in male ratio, 
even though the average mean-temperature of the air and water 
of this vicinity is about as high in September as it is in May or 
June when the male ratio is decreasing. Neither is such mortality 
probable in view of actual experience. One of the writers in 
stocking a pond in Alabama in August, ipi8, carried several cans 
of Gambusia on a railroad journey of about twenty-four hours, 
and on liberating them in the pond, found that a large number 
