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Y. TANAKA. 
mated inter se, will give rise to three forms, zebra, common and plain, in 
the ratio 12: 3: 1, as may be seen from the expression given below: 
C + 2CN f N) X (S + 2 SN + N j - 8 SCN + :i S N + 1SC + 3 CN + 1N. 
1 2 zebra : 3 common : 1 plain 
But such a varying inter-relation supposed by Toyama to exist between 
(S + N) and (C + N appears somewhat complicated and hardly com- 
prehensible. 
3. In a later paper Toyama (1910, a) denotes the common pattern by C, 
the plain by c, and the brown spotted or poly-lunar 15 by P, assuming that 
the poly-lunar is fully developed only in presenee of C- Thus the offspring 
from the cross between poly-lunar and plain will be as follows : 
p PC X cc. 
Poly-lunar Plain 
Pi PCcc 
Poly-lunar 
F, gametes PC, cc, Pc, Cc. 
F, 1 PPCC 4 PCcc + 2 PCPc + 2 PCCc + 2 Cccc + 1 CCcc + 
9 poly-lunar : 3 common ; 
2 Pccc + 1 PPcc + 1 cccc. 
3 faintly spotted: 1 plain 
The above assumption is quite peculiar in as much as it admits the 
formation of such a gametic combination as cc in which two doses of a character 
occur in one and the same gamete. 
4. In his recent work (Toyama, 1912) on the varying dominance of 
certain white breeds, Toyama again touches upon the question of factorial 
constitution of the silkworm. The fact that some European white races 
behave sometimes as dominant and sometimes as recessive to the yellow 
colour was first found and discussed by Coutagne, and later by Kellogg, 
neither of them coming to a clear conception of the case. This paradoxical 
phenomenon found its solution in Toyama’s demonstration that the white 
races used by Coutagne and Kellogg were not absolutely pure, but a mixt- 
1) A larval form provided with a pair of round or lunar patterns on the dorsum 
of each segment. 
