THE MANNER OF OCCURRENCE OF MUTATION 447 
matings were made in successive generations. Each mating was 
Cr Cr 
Dr € 
purple eyes; ¢ = curved wings). More recent experiments have 
shown that a third chromosome mutant was present also, and 
was at least in part responsible for the increased crossing over 
referred to (Sturtevant, ’17). No evidence of the presence of 
any mutant genes in the X chromosome of this line has been 
found, except in the case now to be described. 
of the type oi bp. 69#\\(o0—) black body: ~p.\'— 
TABLE 1 
SECOND CHRO- 
22, 5 Jad, J, ; MOSOME CHARAC- 
parm on coun | 2R-EEp-9o10R | GZ. ern covon | Gt. nym couox | Mma on 
(+ = WILD TYPE) 
February 3........ 20 14 4 2+; 2be. 
WebWeaver) ee 14 10 0 
Hebruary. iS <a. 5. 16 19 1 1+ 
Hebrusry. (Ge. s. 3. 21 20 2 1+; lbe. 
Rebruary: 2. 4/2. 26, 12 12 2 1-+-; Ibe. 
ltlommiay (oececons 9 19 0 
Idelommeiay 10)5 550 ob 14 20 0 
Jnonwaiay WAG ee cos be 16 15 0 
Hebruiany 1422 hee. il¢/ 3 0 
PURO A Sse IRS osu 139 132 9 5+; 4be. 
Culture 4711 was of the type just described, and represented 
the twenty-second generation of brother-sister matings. It 
gave the expected result for the black, purple, and curved char- 
acters; but also gave a few males with a very pale eye color, 
which has been named ivory. These appeared as shown in 
table 1. 
The ivory males which were black and curved certainly also 
carried the factor for purple, just as the other black curved 
males did. One was shown to have it by a breeding test, and 
later results also indicated that ivory and ivory purple are not 
distinguishable. Five of the wild-type females produced by 
4711 (sisters of the ivory males) were tested, but none of them 
gave ivory sons. 
3 See Sturtevant (’17) for the meaning of ‘Cy’ and ‘Cyr.’ 
