50 ILLINOIS ACADEMY OF SCIENCE 
upon the influence of temperature upon the movements of 
fishes. Baird (1886) states that temperature is important in 
influencing the migrations of fishes and Verrill, according to 
Bumpus (1898) says the sudden death of the enormous num- 
bers of "tile fish" in the year 1879 was probably due to a sud- 
den lowering of the temperature of the waters usually warmed 
by the gulf stream. In 1899 Libbey began a series of obser- 
vations to ascertain the connection between changes in temper- 
ature and the migrations of fishes. This investigation was 
merely a continuation of former investigations in which he 
had determined pretty definitely that movements of ocean cur- 
rents and other changes in ocean temperatures are of very 
great importance in these migrations, (Bumpus '98). It is a 
matter of common observation among fishermen that certain 
fishes, for instance suckers, when they ascend the small streams 
in the spring to spawn, often seem to congregate in the warmer 
streams when there are numerous small streams of different 
temperatures to choose from. 
PRESENTATION OF DATA 
In the experiments to be briefly reported here, I have used 
the fresh water fishes of the creeks in the vicinity of Chicago 
and have performed with them two types of experiments, 
namely, resistance experiments and reaction experiments. 
1. Resistance Experiments: These experiments have been 
of two sub-types. (1) Resistance to slowly changing tem- 
peratures, and (2) Resistance to suddenly changing tempera- 
tures. In the first sub-type the fishes were placed in a granite 
pan in about a liter of water (the species used have been small 
except in the case of the bull-head, in which case individuals 
not more than 4 in. long were used), at normal optimum tem- 
perature and the water was then heated gradually. The rate 
of heating was varied considerably in different experiments 
(5 min. up to 1 hr.) In killing experiments the heating was 
continued up to the point where death occurred; in other ex- 
periments the fish was taken out before the death point was 
reached. 
As the water was being heated, the fishes gave very similar 
reactions, specific differences being quantitative rather than 
qualitative. At the beginning, the fish in the experiment swam 
about exactly as did the one in the control. As the experimen- 
tal temperature increased, however, the activity of the experi- 
mental fish increased likewise. This increased activity usually 
became noticeable by the time the temperature in the experi- 
