100 



VICTOR E. SHELFORD. 



against the glass cover more often than in the dry air. This 

 occurred in the cases of Geolycosa and the salamanders. Table 

 IV. shows a greater degree of positiveness for moist than for still 

 air (see Charts I. to IV., pp. 87, 90, 91, 95, central graphs). 



3. Warm Air. 



Table V. shows the effect of raising the temperature upon the 

 humidity and evaporation. The difficulty in manipulating this 

 sort of experiment lies in the fact that the atmometers and the 

 water in the burettes should be at the same temperature as the air 

 used, if results comparable to those at room temperature are to 

 be obtained. This was accomplished approximately, for the 

 purpose of obtaining the data presented in Table V., but the 

 equipment was faulty and the table is probably only sufficiently 

 accurate to give a general idea of the effect of raising the tempera- 

 ture. A rise of 15 to 17 C. is required to double the evaporation. 



TABLE V. 



Showing the effect of raising the temperature upon humidity and evaporation 

 under the experimental conditions. Air pumped from a dry greenhouse. Flow 

 15.6 liters per min.; velocity over the evaporimeters about .104 meter per sec. or 

 0.2 mile per hour. 



(a) Physiological Effect and Reactions. 



The effect of increased evaporation due to rise of temperature 

 is more marked than when the evaporation is due to movement 

 or to dryness. This is probably due to the fact that animals 

 are quite sensitive to temperature alone although the tempera- 

 ture of either air or water has rarely been varied alone and a 

 part of its supposed effect may be due to increased evaporation 

 in air or to decrease in gases in solution in water. 



