Cases of mimic mutations and secondary mutations in tlie X-chromosome &c. \'J 



4. Mutations and gynandromorphs observed during the 

 experiments involving singed. 



Hairy. 



In the cross of an Fi female heterozygous for inflated forked Bar 

 and for singed to inflated forked Bar males CCulture 906, see p. 10) 

 it was observed that some of the females and males had small, irregu- 

 larly distributed hairs on the scutellum and on the head (Dec. 11, 1918). 



Since the character had appeared in females as well as. males a 

 stock was established by mating them together. Tlie new character, 

 which bred true, was called "hairy". 



Hairy did not show any linkage to the sex -linked genes present 

 in the cross from which the haiiy flies were derived. The inflated 

 forked Bar stock bottle was examined and in the next generation was 

 found to contain some hairy individuals, thus indicating that the new 

 character was due to an autosomal recessive gene which had arisen in 

 this stock and for which the female and one or more of the males used 

 in Culture 906 had been heterozygous. 



Hairy flies are characterized by numerous small, irregularly 

 distributed hairs in places which are eötii^ely hairless in the wild fly. 

 These hairs are especially conspicuous on the scutellum and the head. 

 Very useful in classification is a constant group of extra hairs some- 

 what dorsal to the two sternopleural bristles. A peculiar feature is also 

 the presence of small hairs scattered along the veins of the wings, both 

 on the dorsal and on the ventral surface. Extra scutellar bristles are 

 common, the anterior scutellars being especially frequently duplicated 

 on one or on both sides. 



In order to determine to which autosome the hairy gene l)elonged 

 hairy females were crossed to males carrying the dominant characters 

 Star and Dichs;te, Star being in the second chromosome at 0.0 and 

 Dichtete in the third at 38.5. 



Star Dichtete Fi females were back-crossed singly to hairy males 

 (Table 6). 



The result of this back-cross proves that hairj' segregates freely 

 from the second-chromosome character Star and gives 14.9 ^/o of crossing- 

 over with Dichaete. The hairy gene is accordingly located in the third 

 chromosome around 15 units to the left or to the right of Dichaete. 

 Dr. Bridges who has used the character extensively in experimental 



Induktive Abstämmlings- und Vererbungslehre. XXVTII. 2 



