, assimilation is possible, partially at least, without
intermarriage. Instances of this are furnished by the partial
assimilation of the Negro and the Indian of the United States. Thinkers
are beginning to doubt the great importance once attributed to
intermarriage as a factor in civilization. Says Mayo-Smith, "It is not
in unity of blood but in unity of institutions and social habits and
ideals that we are to seek that which we call nationality," and
nationality is the result of assimilation.

2. The Instinctive Basis of Assimilation[242]

It is a striking fact that among animals there are some whose conduct
can be generalized very readily in the categories of self-preservation,
nutrition, and sex, while there are others whose conduct cannot be thus
summarized. The behavior of the tiger and the cat is simple and easily
comprehensible, whereas that of the dog with his conscience, his humor,
his terror of loneliness, his capacity for devotion to a brutal master,
or that of the bee with her selfless devotion to the hive, furnishes
phenomena which no sophistry can assimilate without the aid of a fourth
instinct. But little examination will show that the animals whose
conduct it is difficult to generalize under the three primitive
instinctive categories are gregarious. If, then, it can be shown that
gregariousness is of a biological significance approaching in importance
that of the other instincts we may expect to find in it the source of
these anomalies of conduct, and of the complexity of human behavior.

Gregariousness seems frequently to be regarded as a somewhat superficial
character, scarcely deserving, as it were, the name of an instinct,
advantageous, it is true, but not of fundamental importance or likely to
be deeply ingrained in the inheritance of the species. This attitude may
be due to the fact that among mammals, at any rate, the appearance of
gregariousness has not been accompanied by any very gross physical
changes which are obviously associated with it.

To whatever it may be due, this method of regarding the social habit is,
in the opinion of the present writer, not justified by the facts, and
prevents the attainment of conclusions of considerable fruitfulness.

A study of bees and ants shows at once how fundamental the importance of
gregariousness may become. The individual in such communities is
completely incapable, often physically, of existing apart from the
community, and this fact at once gi