[3.]

Bower, Kerr & Agar. Sex and Heredity. N.Y., 1919, 119 pp.

[4.]

Schäfer, E.A. Nature, Origin and Maintenance of Life. Science, n.s., Vol. 36, pp. 306 f., 1912.

5.

Guyer, M.F. Being Well-Born. Indianapolis, 1916; p. 123.

CHAPTER II