Masculising of females was much more difficult than feminising of males because the testicular tissue was less resistent, and could not be grafted so easily. When it succeeded, however, degeneration of the seminal tubules took place, with increase of the interstitial or Leydig's cells. The vaginal opening in rats disappeared, partly or completely. The sexual instincts became male, the animals recognised a female in heat from one that was not, and attempted to copulate. Steinach considers that he has proved from results that sex is not fixed or predetermined but dependent on the puberty gland. By sex here he obviously means the instincts and somatic characters, for sex in the first instance, as we have already pointed out, means the difference between ovary and testis, between ova and spermatozoa. It is difficult to accept all Steinach's results without confirmation, especially those which show that the feminised male is more female than the normal female. Such a conclusion inevitably suggests that the investigator is proving too much. The subject of the influence of hormones from the gonads is mentioned, but not fully discussed, in a volume by Dr. Jacques Loeb, entitles _The Organism as a Whole_. [Footnote: Putnam's Sons, 1916.] Loeb entirely omits the problem of the _origin_ of somatic sex-characters, and fails to perceive that the fact that such characters are dependent to a marked degree on hormones derived from the gonads, together with their relation to definite habits and functions connected with the behaviour of the sexes to each other, is proof are these characters are not gametogenic, but were originally due to external stimulation of particular parts of the soma. CHAPTER IV Origin Of Somatic Sex-Characters In Evolution