CASTLE: THE HEREDITY OF SEX. 193 
not occur at the formation of its gametes. Nevertheless a mosaic indi- 
vidual does occasionally occur which produces a certain proportion of 
segregated (that is, pure) gametes. Exceptionally a spotted mouse 
when paired with a recessive mate produces pure recessive (white) 
offspring as well as hybrid (dark) offspring. The peculiarity is inherent 
in the parent and is manifested with uniformity by certain individuals, 
but not at all by others. 
IV. Application of the Principles Stated. 
1. DiorciouSs AND HERMAPHRODITE ORGANISMS. 
Sex in dioecious animals and plants is inherited in accordance wi.!. 
Mendel’s law; that is, in accordance with the principles of dominance 
and segregation. The ordinary dioecious individual is a sex-hybrid or 
“‘ heterozygote ” (Bateson), in which the characters of both sexes are 
present, one dominant, the other recessive. In the male, the female 
character is recessive, and conversely in the female, the male character ; 
but each sex transmits the characters of both. 
The existence of each sex (in a latent condition) in the other is 
shown by the occurrence in each sex of rudimentary organs peculiar 
to the other. This evidence is supported by numerous observations 
brought forward by Darwin (’76) to show that an animal in its old age, 
or when its genital organs become diseased, often manifests characters of 
plumage or of voice, or even instincts, which are characteristic of the 
opposite sex. 
But perhaps the strongest evidence of the latency of each sex in the 
other is afforded by the transmission through one sex of the characters 
of the other. Thus, as Darwin states, when the domestic cock is crossed 
with the hen pheasant, the male offspring have the secondary sexual 
characters of the male pheasant; these, manifestly, must have been 
inherited through the female pheasant. 
Again, in many animals which reproduce by parthenogenesis, the 
female bears (without fertilization) both male and female offspring, 
showing that she really possesses both sex-characters. 
Experimental evidence of the latency of one sex in the other in plants 
has been produced by Bordage (98). He cut back the apex of young 
male plants of Carica papaya, just before the appearance of the first 
male flowers. Lateral branches, two on each plant, then arose immedi- 
ately below the cut, and these produced female flowers and fruit. 
