IO4 VICTOR E. SHELFORD. 



volume in the smaller animals. We note further that the animals 

 die after a smaller amount of evaporation when the rate is slow 

 than when it is more rapid. Since the loss in weight of the 

 animals was not determined, it is impossible to state whether 

 it is directly due to differences in the rate of evaporation from 

 the animal and from the atmometer, or to concentration of 

 the body fluids beyond a point compatible with life which 

 resulted in death after a time no matter whether evaporation 

 continued or not. It was noted that after the skin had become 

 dry, the amphibians did not recover even when put into water. 

 However the most remarkable fact brought out by the table is 

 that the animals died more quickly from evaporation due to 

 rapid movement of air than due to dryness. The same is true of 

 evaporation due to higher temperature. Bufo survives longer 

 than Rana. Of the arthropods Pterostichus (ground beetles), 

 Fontaria and Geolycosa die in the order mentioned. The beetles 

 died 22 hours after the beginning of the exposure. 



V. GENERAL DISCUSSION AND COMPARISON. 



The general problems involved in the results which have just 

 been presented are among the more complex of physiology. 

 The relations of the various species studied to their environments ; 

 the relation of kind of integument to survival time in dry air; 

 and the question of reaction and irritability make necessary a 

 rating of the different species and a discussion of the results of 

 previous workers on the physiology of water starvation. 



i. Rating of the Species Studied. 



In order to make comparisons it is necessary to estimate the 

 degree of avoidance of air of the high or low rate of evaporation. 

 In the main there are two indications of reaction ; (a) time spent 

 in the two kinds of air (halves of the cages} and (b) number of 

 turnings back, upon encountering the avoided air. When both are 

 expressed in terms of per cent, of total and the two regarded as 

 of equal value, ratings can be obtained as indicated in Table 

 VIII. (Shelford and Alice, '13). Since the ratings are based 

 upon a small number of experiments, they can be taken only as 

 tentatively representing the relations of the animals to the rates 

 of evaporation. 



