438 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
breeding true for a sex-linked character, the female is homozygous 
for the character in question while the male is heterozygous and incap- 
able of becoming homozygous. Reciprocal crosses with such a race 
give unlike results, because the female transmits the character to all 
her offspring, but the male transmits it to only half his offspring, viz., 
the females. 
Fic. 91.—Sex-linked inheritance of barred and unbarred (black) plumage in 
poultry. P, parents, barred male, unbarred female; F,, barred males and females; 
F., males all barred, females in equal numbers barred and unbarred. (After 
Morgan.) 
2. Poultry type.—Another type of sex-linked inheritance exists in 
which the sex relations are exactly reversed. ‘This was first observed 
in the moth, Abraxas, but more familiar cases occur in poultry, for 
which reason it may be called the poultry type of sex-lnked inherit- 
ance. Here the male is the homozygous sex, the female being hetero- 
zygous. ‘This condition is found in moths and in certain birds, viz., 
