^ GENETIC STUDIES ON THE SILKWORM 
Heterozygous melanic moricaud yellows (MmPPQQBbYy I mated intev sc. 
C 34-3' 1 4 Mel. (B) Choc, (b) Totals 
Mor. yel. MPQY 63 19 82 
Mor. wh. MPQy 39 12 51 
Norm. yel. mPQY 39 16 55 
Totals 141 47 188 
Of which MB 102 : Mb 31 : mB 39 : mb 16 
Exp. ratio 9-3 : 3 : 1 
Opacity. (Opaque, 0, v. transparent, 0. ) 
In ordinary silkworm larvae the skin is, as a whole, powdery white owing 
to the presence of guanin-like granules in the epidermal cells. Only on the 
ventral side, especially the internal side of abdominal legs, on the mid-dorsal 
line over the heart, the cells contain less granules, so that the skin looks more 
or less transparent. There is, however, a strain known as "oily" or trans- 
parent-skinned, in which the white granules are very scanty or entirely absent 
from the epidermis, so that the whole skin is so transparent as to make the 
internal organs and tissues visible from outside with the exception of the 
patterned portions and the opaque hard parts (the head-case etc.). The "oily" 
character is always apparent after the first moult. 
a) Heterozygous knobbed zebra opaque yellows (ZzKkOoyY) mated inter sc. 
A 764' 1 5 A 765' 1 5 
Opaque (0) Oily (0) Opaque ( 0 ) Oily (0) 
Knob. zebr. yel. 
ZKY 
96 
3' 
69 
24 
Knob. zebr. wh. 
ZKy 
33 
10 
30 
4 
Zebr. yel. 
ZkY 
32 
9 
12 
5 
Zebr. wh. 
Zky 
12 
10 
4 
1 
Knob. pi. yel. 
zKY 
30 * 
9 ' 
24 * 
6* 
Knob. pi. wh. 
zKy 
'4* 
0 
8 : ' : 
j 
PI. yel. 
zkY 
6 * 
0 
6 * 
2 * 
PL wh. 
zky 
5 * 
0 
0 
0 
