"The warlike duty of defense is also borne chiefly by males, and must often be an immense tax on the energies."

“Whenever man does not interfere, monogamy seems to be the general order of Nature with all higher organisms.”

“Other things being equal, the law seems to be directly reversed.”

“Every action, physical or psychical, involves either integration or disintegration.”

“Popular Science Monthly, New York, September 1874”

“In women, if there is a greater arrest of individual growth than in men, the difference begins in the fœtal life; their comparative weight and size at birth are the same as at maturity; and, if the former finish their growth earlier, it must be because relatively they grow more rapidly.”

“Every action, physical or psychical, involves either integration or disintegration; every use of faculty belongs to the latter class. There is no more antagonism between growth and reproduction than between growth and thought, growth and muscular activity, growth and breathing.”