Steinach in another series of experiments castrated young male rats and transplanted into them the ovaries of young females. These ovaries did not disintegrate, the eggs remaining, and corpora lutea were formed. In such feminized individuals the seminal vesicles, prostate, and penis did not reach their normal development, and it was thereby proved that the internal secretions from the ovary do not promote the growth of the secondary sexual male characters. On the contrary, Steinach was able to show that the growth of the penis was directly inhibited by the ovary, since in the feminized males this organ remained smaller than in the merely castrated animals. On the other hand the infantile uterus and tube when transplanted into the young male with the ovaries grow in a normal way, and Steinach thinks that pregnancy in such feminized males is possible if sperm be injected into the uterus. In some regards the feminized males showed the morphological habitus of females. Soon after the transplantation of ovaries into a castrated male the nipples of its mammary glands begin to grow to the large size which they have in the female and by which the two sexes can easily be discriminated. In addition the stronger longitudinal growth of the body in the male does not occur in the feminized specimens, the body growth becomes that of a female; and likewise the fat and hair of the feminized male resemble that of a real female. While the castrated males show an interest in the females, the feminized males are absolutely indifferent to females and behave like them when put together with normal males; and, what is more interesting, they are treated by normal males like normal females. The sexual instincts have, therefore, also been reversed in the feminized males by the substitution of ovaries for testes. The inhibition of the growth of the penis by the ovary is of importance; it supports the idea already expressed that in hermaphrodites this inhibition of the growth of the secondary organs of the other sex is only feeble or does not exist at all. We may finally ask whether there is any connection between the cytological basis of sex determination by special sex chromosomes and the physiological basis of sex determination by specific substances or internal secretions. It is possible that the sex chromosomes determine or favour, in a way as yet unknown, the formation of the specific internal secretion discussed in the second part of this chapter. In this way all the facts of sex determination might be harmonized, and it may become clear that when it is possible to modify secretions by outside conditions or to feed the body with certain as yet unknown specific substances the influence of the sex chromosomes upon the determination of sex may be overcome. CHAPTER IX MENDELIAN HEREDITY AND ITS MECHANISM[200] _I_