"8 



THE AMERICAN NATURALIST [Vox,. XLIX 



every 152 flies. But 89 of these abnormals were flies with beaded 

 wings. This character is very variable; some of the flies had 

 only a few bristles missing from the margin of the wings, while 

 others had both the outer and inner margins of the wings ser- 

 rated. The character has been recurring in the stock so fre- 

 quently that it can scarcely be ascribed to outcrossing. Many of 

 these flies were mated, but they either did not leave offspring, 

 or the character did not reappear in the F 2 generation. 



The three gynandromorphs arc nol to he considered as mu- 

 tants. The data here show that gynandromorphs occur once in 

 about five thousand jive hundred times. 



Flies with truncate wings are of occasional occurrence in the 

 laboratory stock, as are also those with abnormal abdomen; hence, 

 flies with these characters are not to be considered as due neces- 

 sarily to the outcrossing. The truncate would not breed and the 

 abnormal abdomen character did not reappear in the F 2 genera- 

 tion. If a character does not reappear in the F 2 generation it is 

 considered to be of somatic and not of germinal origin, unless 

 an environmental condition is necessary for the expression of 

 the changed character. 



The abnormality of the fly with five legs may have been the 

 result of accident, for the character did not reappear in the F, 

 generation. 



Three characters were found to be inherited ; the one called 

 "furrowed," which arose from the cross of black pink bent with 

 wild stock from Massachusetts: the one with a projection from 

 the posterior cross vein toward the base of the wing, called 

 " tau," which arose from the cross of black purple vestigial arc 

 speck with wild stock from Illinois; but since this stock had 

 just been received from Illinois, and since the character appeared 

 in four of the flies, it is suspected that the character was reces- 

 sive in the wild stock and not due solely to the cross. Also from 

 cherry club vermilion crossed to stock from Arkansas arose two 

 males with three cross veins on the wings and a disturbance of 

 the ommatidia of the eye. This character is called " warty." 



Pure stocks of flies with these characters have been bred for 

 many generations and each continues to breed true. " Warty " 

 has many other characters than the modification of the eyes, 

 e. g., beaded wing, spread wing, from two to five cross veins 

 on the wings, abnormal abdomen and disarranged hairs on 

 the thorax. The females are sterile and the race is maintained 



