2OO MILDRED HOGE RICHARDS. 



precautions all of the flies died if the temperature was allowed to 

 rise above 33. 



Although from the standpoint of its original purpose the 

 experiment, due to inadequate apparatus, was not entirely suc- 

 cessful, a number of interesting things resulted from it. Ab- 

 normalities of various kinds appeared in the second generation of 

 incubated flies. In one case, after the first generation had been 

 developed in the incubator, some of the progeny (Fi) were bred 

 at room temperature, and among the 2 so obtained arose the 

 scarlet eye color. 



The temperature experiments were carried on for seven genera- 

 tions; and in each variations appeared. Most of these were 

 peculiarities of the wings, but there were also modifications of 

 eye and leg characters. Among the wing peculiarities were the 

 following: short wings, wing edges turned up, wings folded at the 

 tip, wings bent at abnormal angles, wings spread similar to 

 "spread" of the third chromosome, and wings of odd shapes. 

 Still other flies had weak legs, bent between the joints, and one 

 fly had small eyes. 



In each case the variant was allowed to mate with a wild fly 

 at room temperature. The FI were divided into two lots, one 

 of which reproduced at room temperature and the other in the 

 incubator. It was hoped in this way to perpetuate the variations, 

 should any of them be germinal. Many of the flies were non- 

 viable or non-fertile, but in those cases where 2 were obtained 

 they were usually normal, and the abnormals which did appear 

 were not like those of the original parent. 



Only one color variation appeared. It proved to be germinal 

 in character, and has given rise to the strain called scarlet. 



Scarlet is a bright color, like the vermilion of the first chromo- 

 some, in flies that are newly hatched. As the flies get older the 

 color gradually changes, and in old flies it is almost indistinguish- 

 able from the wild red type. In all crosses where scarlet is 

 used it is highly important, therefore, to count the flies immedia- 

 tely after hatching. 



Scarlet was crossed with a member of each of the four groups 

 of linked genes in order to determine its linkage. Crosses were 

 made with blood of the first chromosome, with vestigial of the 



