442 



FRANCIS M. BALDWIN. 



This is due to the fact that it is difficult to control the environ- 

 mental temperature throughout the whole period, although in 

 general, the trend of increase and decrease is fairly definite. 



2.30 



3.30 



FIG. 5. Plot showing the average body temperature fluctuations of five painted 

 turtles correlated with environmental rise. 



The snapping turtle, in experiments under similar conditions, 

 seems to indicate the same general trend, although these animals 

 apparently do not increase in body temperature as rapidly, 

 especially during the initial rise of environmental temperature as 

 does the painted form. This slight difference, however, is 

 transient if the increase in environmental temperature is steady, 

 and eventually at the high critical points the body temperature 

 as well as the reactions in this form simulate those in the other 

 form. Data averaged and plotted from four individuals and 

 checked against the environmental rise are shown in Fig. 6. 

 It is noted on comparison with the preceding plot that increments 

 of environmental temperature are not quite as effective in 

 raising the body temperature in the snappers as in the painted 

 variety. On anatomical grounds one is tempted to attribute 

 these differences in part to a greater radiating surface of soft 

 parts exposed in the snappers, for it is well known that the 

 relative extent of the plastron in this form is considerably less 

 than it is in the painted form. Whether there are in addition, 

 physiological differences in the two forms can not at this time 



