Here again, as in the two sides of the body, appear, surely, the factors of Dominance and Recessiveness—in other words of Maleness and Femaleness; of strength and activity upon material planes, and of inhibition upon these.
Developments which, being in full agreement with one another and with others, suggest that the two orders of Sex-characteristics (derived from parents of opposite sex) are centred, respectively, in the two sides of the body, and in the two brain-hemispheres allied, respectively, with these. One side of the body, with its allied brain-half, represents the paternal inherences of the individual; the other, the maternal. If so, the right side of the body, with its allied Leading, or Dominant, brain-half is, clearly, of male inherence. While the left side, with its allied Recessive, or Dormant, brain-half is of female inherence.
The inference is further supported by the fact that the stronger right side is rather larger and more masculine in form; while left-side limbs are in normal right-handed persons, more slender and shapely and delicate—in a word more womanly—than are those of the right.
As regards the face, from one aspect both sides are complete, from another aspect both are incomplete, without the other. And in configuration and expression, the two sides of the face differ appreciably; the left side being more psychical, emotional and subtle—in a word again more womanly.
In most persons, the hands and ears and eyes of one side differ from those of the other, both in form and in function. In some persons the differences are considerable. It happens occasionally, indeed, that the eye of one side resembles in colour the eyes of one parent, while the opposite eye bears the colour of those of the other parent.
Strange to say, there are, moreover, in the human male, organs concerned with the strictly female function of lactation.
Indication of primæval human hermaphrodites formed one of Darwin's greatest puzzles, indeed. In his Descent of Man, the following passage occurs:
"It has been known that in the vertebrate Kingdom one sex bears rudiments of various accessory parts appertaining to the reproductive system, which properly belong to the other sex.... Some remote progenitor of the whole vertebrate kingdom appears to have been hermaphrodite, or androgynous."
It escaped him as it has escaped later biologists that Man, the highest of the vertebrates, is still androgynous. And this inevitably so, since, being of bi-sexual parentage, the sex-characteristics of both parents must be present in him.
In The Evolution of Sex, Professors Geddes and Thomson state: