SEVENTH ANNUAL MEETING 57 



changes to lower temperatures may be due to a failure of the 

 mechanism to adjust to the extreme change. This explanation 

 is supported by the fact that more adjustment was made in the 

 case of slow heating than in the case where heating was rapid, 

 and also by the fact that complete adjustment took place when 

 cooling was slow. Thus acclimatization to temperature may 

 be looked upon as resulting from an adjustment of the temper- 

 ature regulating mechanism. 



Experiments upon the rate of metabolism under different 

 temperature conditions have not been carried out as yet. Just 

 how the rate of reaction is affected, for instance, by raising 

 the temperature of the water surrounding a fish is not certain. 

 It is probably correct to state that in general the rate of meta- 

 bolism is increased with increase in temperature, and dimin- 

 ished with decrease. But whether or not each degree's rise or 

 fall in temperature increases the carbon dioxide output to the 

 same extent is a question. Very probably the effect upon the 

 metabolism, of changes in temperature is not the same at dif- 

 ferent points in the temperature scale, that is to say, the meta- 

 bolism of a fish at 3° C. may differ from its metabolism at 

 25 °C, not only quantitatively but qualitatively as well. Fur- 

 thermore the factors that cause the fish to pass into a state of 

 uncontrolled convulsive activity at the stages of heat and cold 

 rigor and what heat and cold rigor are in themselves, are ques- 

 tions that can be answered only by means of quantitative ex- 

 periments which are yet to be undertaken. At this time it 

 seems plausible to look upon these reactions as outward mani- 

 festations of qualitative or cumulative quantitative changes in 

 the metabolism of the organism. 



TEMPERATURE AND THE DISTRIBUTION OF FISHES 



It is interesting to find that forms where the activities of the 

 individuals are so dependent upon the conditions of the sur- 

 rounding environment, possess exceedingly delicate mechan- 

 isms for the detection of environmental changes. Thus it has 

 been shown that they are able to recognize very minute dif- 

 ferences in acidity, (Shelford and Allee, '13), (Shelford, '14) 

 and in the foregoing pages we have seen that they are also ex- 

 ceedingly sensitive to slight changes in temperature, their sen- 

 sitiveness in this respect far exceeding that of warm blooded 

 animals. This fact becomes a suggestive one when thought of 

 in connection with the life activities of fishes and the resulting 

 distribution of these forms through their reactions. (The 

 relation of resistance to reaction has been discussed in a former 



