of seed, and in most of those orders of animal life below the mammals, by means of the egg. Both of these methods, however, with the elaborate processes of which the seed or egg is the immediate agency—and has its analogy in mammalian reproduction, including the human-are definitely sexual.
The lower forms are interesting in tracing the steps of biological reproduction up to the higher and more complex forms of life. In sex we find the essential touch of nature that makes the whole world akin, that affords the impetus to the preservation of life and that is, as well, in the higher forms of life, when the consciousness of sex becomes evident, the source of much joy and ecstasy.
Among the lower forms of life, the rôle of sex seems to be the focal center of all life's activities. Everything else, even the search for food, and the preservation of the individual life, may be subordinate to and revolve around the pivot of reproduction.
In the case of certain insects, for instance, the whole development of the individual's life is an elaborate preparation for reproduction—as it is, in fact, throughout all of nature—and when this is accomplished the life-function of that individual has rendered its sole service to the species and comes to an end.
Sexuality Becomes More Complex. As we follow the higher forms in the biological scale of life, however, sex expression becomes more and more a specific act, periodic or occasional, instead of the almost exclusive function of life.
But even where the sex act itself becomes an occasional or periodic function, there are in evidence numerous secondary characteristics of sex which constantly assert themselves without denoting a conscious sexual impulse or response.
These secondary sexual characteristics are both physical
