No. 583] ROLE OF ENVIRONMENT IN DROSOPHILA 413 



The daughters were either heterozygous for Mack or pure 

 black, likewise the sons. Hence, direct comparison could 

 be made. The following protocol gives the results for 

 four successive counts: 



1. Black $ quite abnormal. Intermed. $ quite abnormal. 

 Black J quite abnormal. Intenned. J quite abnormal. 



2. Black 5 quite abnormal. Interna,]. $ quite abnormal. 



3. Black $ fairly abnormal. Inten L $ fairly abnormal. 



Black J very abnormal. Intenned. J very abnormal. 



4. Black $ none present. [ntermed. $ fairly abnormal. 



The evidence shows no difference between the extent of 

 development of abnormality in the homozygous black and 

 heterozygous black females and males. 



In another way an attempt was made to get light on the 

 same question. Ked black females were mated to white 

 abnormal males ; and, simultaneously, red gray females 

 were mated to white abnormal males. The females were 

 later put into the same bottle and their offspring reared 

 together. All the daughters for four counts were normal. 

 At the fifth count an attempt was made to separate the two 

 classes of daughters, which is possible, because the off- 

 spring heterozygous for black are darker than the grays. 

 The heterozygous pairs were normal or slightly abnormal 

 while the pure grays appeared a little more abnormal; 

 but the difference is hardly to be relied upon, since the 

 abnormality is less striking in the black flies. 



To test this possibilty some of the preceding experi- 

 ments were carried to F 2 , when pure abnormal grays, in- 

 termediate and pure abnormal blacks appear. The most 

 abnormal grays were no more abnormal 

 normal blacks, which so far as it goe 

 homozygous black flies themselves may be as almoi 

 the grays under the same conditions and with tli 

 ancestry. 



that 



