336 



mean temperature for each minute of a ten-minute schedule and reading 

 the mean velocity for each minute from the curve in Fig. 3, as follows : 



Thus, with an accumulation of 60.5° of "eiifective temperature." a 

 total distance of 70.4 progression units, or 3290.33 mm., was traveled in 

 those 10 minutes of variable temperature; but a comparison of column 3 

 and column i shows clearly that the "efifective temperature" is not a cor- 

 rect index of the rate of travel or of the distance traveled above 28° C. or 

 below 22° C. (i.e., outside the straight-line limits). Only in the 10th 

 min., with the temperature at 25° C. (i. e., within the straight-line limits) 

 does the "efifective temperature" properly indicate the rate of travel. 



The development of the codling moth in its several stages, and in 

 fact, the behavior of nearly all other organisms hitherto investigated* 

 with respect to diflferent temperatures, is similar to the activity of the 

 milliped. In a developing organism, however, the processes involved in 

 growth, transformation of parts, etc., do not go on at the same rate at 

 different times within the same stage, and thus only fractions of a whole 

 process are usable as developmental units. Various results of the stimula- 

 tion of organisms by temperature do bear a definite ratio to the tempera- 

 ture within the straight-line limits of the velocity curve, although not 

 outside those limits. 



Further evidence of the nature of development is found in the fact 

 that the total carbon-dioxide given off by an organism such as the pupa 

 of the meal worm is a constant for individuals of the same weight. This 

 total bears a fixed ratio to the sum of the daily amounts of development 

 of the pupa, but not to the "effective degrees" summed above a definite 

 beginning (an imaginary "threshold," which is the hyperbolic zero) ex- 



• Shapley ('20) has a curve for progression of ants which appears to be excep- 

 tional in that it turns upward .it hiKh temperatures. 



