On the zygotic constitution of dominant and recessive whites etc. 235 
number Cocoons produced 
Parentage of matings = 
reared white yellow total 
No. 4 (34 class) . 13 4,148 926 5,074 
No. 4 (4t class) . 14 3.652 934 4,586 
No. 4 (sth class) . 10 2,237 581 2,818 
No. 4 (6th class) . 15 4,253 930 5,183 
Total: 52 14,290 (80.9%) 3,371 (19%) | 17,661 
Expectation : u 81.25% 18.75% _ 
Notwithstanding the fact that the cocoon colour of the parent 
moths was different, each mating gave white and yellow cocoons in 
the approximate proportions 13 W (81.25 %):3 Y (18.75 %). Among the 
F, white cocoons, as in the F,, we again observed individual cocoons 
of various shades. 
The proportion of 13 whites : 3 coloured had already been obtained 
by KEEBLE and PELLEW (8) in Primula sinensis when they crossed 
various coloured forms with a white form called „Snow King“ and 
thus the presence of both dominant and reccesive whites in the 
Snow King was proved. GREGORY (5) found similar facts in Primula 
sinensis. BATESON and PuUNNETT (I) also found both dominant and 
recessive whites in poultry. Miss SAUNDERS (10) demonstrated domi- 
nant and recessive whites in Digitalis purpurea. EAST (4) also 
observed similar facts in blue aleurone colour in some maize. SHULL’s 
observations (II) on the corosses of various forms of Zychnis and 
Papaver came in the same category. 
As to the cause of dominant and recessive whites, as BATESON, 
PUNNETT, and others had demonstrated, it is considered to be due 
to the presence of a factor which prevents the development of colour. 
If we represent the presence of this factor by ss and its absence by 
ss, and the presence and absence of yellow colour by YY and yy, the 
dominant white of the silk-worm will be SSYY (first dominant) or 
SSyy (second dominant), the recessive white ssyy, and the yellow ssYY. 
If inbred, all of them will breed true to parents. 
16* 
