PROCEEDINGS 
• OF THE 
NATIONAL ACADEMY OF SCIENCES 
Volume 4 MARCH 15, 1918 Number 3 
THE EFFECT OF ARTIFICIAL SELECTION ON BRISTLE NUMBER 
IN DROSOPHILA A MPELOPHILA AND ITS INTERPRETATION 
By Fernandus Payne 
Zoological Laboratory, Indiana University 
Communicated by H. S. Jennings, January 7, 1918 
About two years ago I began an experiment to test the effect of artificial 
selection in a bisexual form. Drosophila ampelophila was chosen after a 
careful search through the list of material which could be bred in the lab- 
oratory. There were two principal reasons for using this material. First, it 
is easily bred, and second, because of the four sets of linked genes described 
by Morgan and others, it is possible to better interpret how the results of 
selection have been accomplished. I wish to emphasize that the interpre- 
tation of the results is the important part of the problem. Practically every 
one admits that selection may be, in certain cases, effective. 
The present work is not a repetition of McDowell's, although the character, 
bristle number, has been used. He used the bristles on the thorax, while I 
have used the bristles on the scutellum. Some of our final conclusions may 
agree, yet, the work is very different and I believe my own conclusions have 
been carried to a more definite termination. McDowell did not attempt to 
link up the factors which he believed the cause of extra bristle number with 
any other genes. 
The experiment was started by mating a female with one extra bristle on 
the scutellum to a normal male (four bristles is the normal number). Both 
flies were taken from a mass culture which had been kept in the laboratory 
for about three months. Counts in this mass culture before the experiment 
began gave 612 normal flies and the one female with one extra bristle. The 
result of this cross (female five by normal male) was 226 normal flies and two 
females with one extra bristle. These two Fi females with one extra bristle 
were mated to Fi normal brothers. These two pairs gave F 2 offspring as fol- 
lows: 935 normal, 39 with one extra bristle, and four with two extra bristles, 
a ratio of extras to normals of 1 : 21.7. From these F 2 offspring, the flies with 
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