426 



EFFECT OF TEMPERATURE UPON FACET NUMBER 



further on this point. My values for the length of the egg-larval-pu- 

 pal period do not coincide in some particulars with his, due to a differ- 

 ence in technique. My flies were subjected to the experimental tem- 

 peratures immediately upon mating. 



With my cultural methods, I was unable to get the Ultra-barstock 

 to develop beyond pupation at 33° C. The data given in the develop- 

 mental curve for this temperature are for wild full-eyed stock. There 

 is some variation in the length of the periods as shown by the indi- 

 vidual cultures. All sets made up at the same time and with the same 

 food, however, give the type of curve shown by the averages (Table 

 XII). 



TABLE XII. 



Efect of Temperature upon the Length of the Immature Period (Egg-Larval-Pupal) 



in Drosophila. 



In Fig. 9 is shown the number of days from mating of the parents 

 to the emergence of the offspring from pupation. The reciprocal, or 

 rate per day, curve is also given. This rate curve gives approximately 

 a straight line between 15 and 29°C. Beyond 29° it turns down, thus 

 showing an optimum. 



This type of temperature curve is found for nearly all physiological 

 reactions. Krogh has recalculated Loeb's data and has shown that 

 they represent the time-temperature relations for the rate of segmen- 

 tation of the sea urchin eggs far better than the van't Hoff formula. 

 In the experimental data of various workers he has demonstrated this 



