Vol. 6, 1920 
GENETICS: C. B. BRIDGES 
661 
distant as vermilion {v locus, 33.0). The next step was to mate a cross- 
veinless forked small-eye male to a vermilion female and to raise several 
F2 cultures (table 1). 
TABLE 1 
Pi, Crossvdinless Forked Small-eye X Vermilion 9 ; Fi Wild-Type 9 , 
cv f sy 
X Fi Vermilion (Table Includes F2 & Only) 
V 
0 
1 
2 
3 
1,2 
1,3 
JAN. 20, 
1920 
cv f sy 
V 
cv V 
/ sy 
cv 
V f sy 
cvf 
V sy 
cv V f sy 
+ 
cv V sy 
/ 
11223 
64 
60 
19 
15 
22 
17 
3 
1 
1 
1 
11225 
41 
63 
16 
19 
18 
10 
1 
1 
2 
11226 
42 
52 
16 
14 
25 
14 
2 
2 
1 
2 
1 
11227 
63 
62 
18 
10 
19 
16 
1 
2 
1 
11268 
102 
84 
29 
24 
39 
31 
1 
1 
4 
4 
11275 
89 
110 
31 
27 
27 
33 
1 
3 
2 
3 
11276 
10 
22 
3 
4 
5 
8 
1 
2 
1 
Total 
411 
453 
132 
113 
155 
129 
9 
8 
9 
16 
2 
1 
The locus of crossveinless, on the basis of the F2 males, proved to be 
about 19.0 units to the left of vermilion, that is, about 14 units from the 
zero end of the chromosome. This location is regarded as especially 
valuable since the interval from ruby (7.5) to cut (20.0) did not contain 
any serviceable mutant character. The rather poor mutants club (16.7), 
lemon (17.5), shifted (17.8), and depressed (18.0) had all been lost or dis- 
carded. It was important to have a mutant of first rank in this region 
in order to investigate the linkage behavior of lethal-2, which is probably 
a "deficiency." A multiple stock, ruby cut tan (/, 27.5) vermilion had 
been made up for this analysis, and it was decided to incorporate the 
crossveinless character in the multiple. In the process of incorporating 
crossveinless, accurate knowledge of the location of crossveinless was 
obtained from the F2 results of the cross between crossveinless male and 
females of the original multiple (table 2). 
There was 8.5% of crossing over between ruby and crossveinless, and 
8.3% between crossveinless and cut. The locus of crossveinless is thus 
almost exactly in the middle of the gap between ruby and cut. The 
total amount of crossing over between ruby and cut was 16.8 which is 
slightly higher than the expected value 12.5. 
This position of crossveinless makes it possible to study linkage rela- 
tions in any part of, or throughout the X-chromosome, by means of 
mutants so close together than no unobserved double crossing over occurs. 
Furthermore, these mutants are perfectly classifiable in combination, 
and, with the exception of cleft at the extreme right end of the chromo- 
