higher social morality. All that we can say in a
general way concerning the complex entanglement of our sentiments and
instincts is that, the most deeply rooted characters in human nature
are at the same time, phylogenetically speaking, the most ancient.

Among the most profound instincts of sexual life, we find moral and
intellectual incongruities. Along with excitement of the sexual
appetite in the male by the odor of the female genital organs, or by
the sight of erotic pictures, we find the most touching conjugal love,
and life-long devotion of one conjoint for the other and for the
children. Prostitution, marriage by purchase, religious marriage,
disgrace attached to illegitimate births, conjugal and family rights
of one or the other sex, etc., are, on the contrary, things which do
not depend on recent phylogeny, but only on the customs and traditions
of certain races. They are partly outgrowths from egoism, the spirit
of domination, mysticism and hypocrisy, and partly the shifts of an
overheated social life which is becoming more and more complicated.

Westermark's studies are very instructive in this respect. All the
absurdities and contradictions, brought to light by the historical and
ethnographical study of the customs and matrimonial abuses in man,
allow us to clearly distinguish that which is due to fashion or
custom, from that which is deeply rooted in our heredity. To avoid
repetition I refer my readers to Chapter VI, to examine the
differences between heredity and custom.

Between these two extremes there is, however, one important domain,
viz., that of _recent phylogeny_, or in other words _variation_. The
fixed appetites and instincts of the species which are proper to every
normal man, and are as we have seen fundamentally connected with many
animal forms, belong to ancient and profound phylogeny. But there is
another group of very variable peculiarities, strongly developed in
some men and little in others, sometimes completely absent, which do
not depend on custom but on what is called individual hereditary
disposition, or individual character. While some men have monogamous
instincts others are polygamous. Some men are by instinct and heredity
very egoistic, others more altruistic. This peculiarity is reflected
in their sexual life and changes the character of their love (but not
that of their sexual instinct). The egoist may love his wife, but this
love is interested and very different from that o