170 



E. W. SHYSTER. 



average facet number was decidedly lower than that of the 

 parents. In the male flies this difference was 26, and in the 

 female flies 35. A count of the stock was made at the end of the 

 experiment, and it was found that here the facet number had 



TABLE II. 



EXPERIMENTS i, 2, 3. FEMALES. 



increased, the average for the males being 50 higher than that 

 of the parents, and for the females 30. Previous to the time of 

 the experiment, the stock had been kept in a room where the 

 temperature was approximately 2i-23, while, during the time 

 of the experiment, it was kept at I9-2I. 



Experiment 4 (Tables III., IV.). Experiments I, 2 and 3 



TABLE III. 



EXPERIMENT 4. MALES. 



indicated that temperature is an important factor in facet varia- 

 tion. To test this more fully one set of Drosophila was placed 

 in an incubator, where the temperature was 28.5, another was 

 kept at room temperature, 22, and a third set was placed on 

 a cold plate at 17.5. The offspring were then allowed to 



