662 GENETICS: C. B. BRIDGES Proc. N. A. S. 
TABLE 2 
Pi, CROSSvmNLESs X Ruby Cut Tan Vermilion 9 ; Fi Wild-Type 9 , 
cv 
X Firb a tv (Table Includes F2 & & Only) 
0 
1 
2 
3 
4 
1,3 
1,4 
2,3 
2,4 
FEB. 14, 
rb 
rb 
rb 
rb 
rb 
rb 
)-& 
1920 
cv 
cv 
CV 
cv 
cv 
cv 
a 
ct 
ct 
Ct 
ct 
ct 
t 
t 
t 
t 
t 
t 
i 
t 
V 
V 
V 
V 
t 
V 
V 
V 
11328 
63 
87 
6 
15 
17 
14 
10 
7 
7 
7 
1 
11329 
62 
74 
12 
6 
8 
7 
7 
5 
8 
5 
1 
2 
3 
1 
1 
1 
11330 
75 
77 
6 
5 
7 
4 
10 
9 
6 
6 
1 
11331 
86 
74 
15 
4 
8 
5 
9 
9 
7 
7 
11332 
72 
87 
5 
8 
6 
12 
10 
6 
2 
17 
1 
11333 
75 
77 
10 
8 
10 
7 
10 
6 
10 
6 
1 
11400 
47 
44 
4 
8 
4 
4 
5 
2 
5 
5 
11418 
59 
70 
10 
5 
9 
8 
5 
8 
3 
2 
1 
1 
Total 
539 
590 
68 
59 
69 
61 
66 
52 
48 
55 
3 
3 
4 
1 
2 
2 
some, are of such excellent viability that they can be used simultaneously 
with only negligible differential mortality. Crossveinless is one of the 
best of these characters, since the somatic effect is so slight that inter- 
ference with the classification of other mutants is at a minimum. It is a 
matter of observation that mutants like crossveinless with slight somatic 
effects are generally those with least disturbance to viability. A striking 
example of this correlation is to be found in the cut mutations. On at 
least eleven occasions sex-linked mutations that were similar to the origi- 
nal cut have appeared. Of these, cut^ was both the poorest in viability 
and the most extreme in extent and number of somatic changes, while 
cut^ was the best in viability and least extreme in its single observed 
somatic change. Two of the other allelomorphs, were intermediates in 
table 3 
Pi, Crossveinless 9 X cuT^ d"; Pi Wild-Type 9, , X Ficvd {F2 & & Only) 
APR. 14, '20 
cv 
ct^ 
CV cf^ 
-f- 
CONT. 
cv 
ct^ 
cv ct^ 
+ 
11700 
88 
95 
9 
8 
11733 
228 
235 
15 
14 
11701 
81 
75 
7 
7 
11734 
143 
164 
11 
12 
11702 
108 
106 
7 
10 
11735 
89 
88 
6 
7 
11703 
22 
26 
2 
2 
11736 
135 
156 
7 
12 
11704 
91 
88 
4 
5 
Total 
985 
1033 
68 
77 
