jJTOSHIMARO TAN AK A t 87 
inheritance (Sturtevant, 1915 b). Sex-limited inheritance is explicable on 
the assumption that the female sex is the bearer of the linked character in 
some cases, and the male in others. Such a parallelism between sex-linked 
inheritance and linkage of non-sex-linked characters appears much interesting 
as well as suggestive. 
V. NON-CORRELATED CHARACTERS. 
The Mendel ian factors concerned in the present experiments are eleven in 
all, i. c. S, M, P, Q, Z, L, K, 0, B, T and Y. l) Of these 1 1 factors the follow- 
ing 55 combinations are possible : 
Of the combinations 
shown in the left, those con- 
nected by dotted lines have 
not been tested yet, while 
those factors connected by 
thick lines are correlated 
either positively or nega- 
tively in inheritance, and 
were described in the preced- 
ing pages. All other combi- 
nations show those which 
are transmitted independent- 
ly of each other. 
It may be interesting that there are so many independent characters in 
the silkworm which has chromosomes as numerous as 2S in haploid (Yatsu, 
191 3), while In Drosopkila, in which only 4 chromosomes are present in 
haploid condition (Stevens, 1908), all the tested characters fall into 4 groups 
of linkage. 
1) Besides these, multiple factors are assumed for the normal and quail patterns, moulting character, 
etc. (See Chapter VI ) 
