EYE FACET NUMBER IN DROSOPHILA MELANOGASTER. 173 



develop has little, if any, effect upon the facet number of the 

 offspring. 



Experiment 5 (Tables IX., X.). This experiment is the most 

 conclusive as a high temperature of 29 and a low temperature 



TABLE IX. 



EXPERIMENT 5. MALES. 



of 17.5 were maintained throughout. The male flies developing 

 at the low temperature showed an average facet number three 

 times as great as that of those developing at the higher tempera- 

 ture, the corresponding ratio for the female flies being 4.7. 

 The average facet number of the male flies developing at 29 

 was 56, of those developing at 17.5, 167; the average facet 



TABLE X. 



EXPERIMENT 5. FEMALES. 



number of the females developing at 29 was 27, of those de- 

 veloping at 17.5, 128. The parents of the above sets, developing 

 at 22 showed little difference in the average facet number. In 

 the males this difference was 2 facets, in the females it was 10. 

 In both males and females the parents which had the higher 

 facet average gave offspring with the lower average, these being 



