BRISTLE INHERITANCE IN DROSOPHILA 



87 



upon the condition of the food and the environment. The 

 similarity in the occurrence of decreased bristles and decreased 

 size at the last of a bottle led to the idea that there might be 

 some relation between the two phenomena. To see if smaller 

 flies are apt to have fewer bristles, the total body lengths of 

 1400 random flies have been measured and their bristles counted. 

 The data have been arranged in correlation tables. From table 

 13 one finds that up to a certain body size there appears a sort 

 of correlation, in that the smaller the fly, the fewer the extra 

 bristles it is apt to show. Above this size (grade 500) there 



TABLE 13 



Males and females. Correlation between size and numbers of extra bristles 



appears to be no constant relation between the increase in size 

 and the numbers of extra bristles. However, it will be noted 

 that above this size there are no normals. It has been concluded 

 that the factor controlling extra bristles is not sex linked; how- 

 ever, nearly all the curves of extra bristled flies that have been 

 presented, have shown that the males have fewer bristles than 

 the females. Correlation tables were made for males and 

 females separately (tables 14, 15). These show strikingly 

 enough, that the males have fewer bristles than the females and 

 are smaller, no male being above grade 500. This does not mean 



