_Sexual, Puberty or Interstitial Glands_)

The gonads is the name applied to the generative or reproductive
glands considered collectively. In the male, they are the testes; in
the female, the ovaries. They are, therefore, sometimes called the
sexual glands. As they possess definite canals for the removal of
their gross secretion, the specific reproductive cells, ova or
spermatozoa, to a surface of the body, they are first of all glands of
external secretion. But they have been also found to hold secretory
cells not concerned with the making of the reproductive corpuscles,
but, as all the evidence indicates, with the manufacture of an
internal secretion. These interstitial cells form the interstitial
gland. A classic example of a gland of internal secretion lodged in
the interstices of a gland of external secretion is thus furnished by
the gonads.

ORIGIN OF SEX TRAITS

The history of sex goes back far in the scheme of life. The
immortality of the ameba was at one time one of the indisputables of
biology. Then some observations were made which threw doubt upon a
long accepted fact, now declared a dogma. Lately, opinion has veered
back to immortality. But in the case of a close relative of the ameba,
the one-celled animal known as the paramecium, union with another
paramecium, true conjugation, has been proved necessary to prevent
death sooner or later. Sex here appears in its most primitive form, on
the basis of exchange of necessary materials, between individuals to
prevent death, their own having been, so to speak, worn out, in the
course of metabolism.

Specifically different sexes come later, when mortality is a universal
fate, as a means of rebirth and escape from death. Then the sexes
develop their latest function, most prominent among the younger
vertebrates, of acting as nature's most potent method of variation and
differentiation. In the pursuit of the different, nature has exalted
sex, and the intensity of the sex life. As far as the preservation of
a species is concerned, and the reproduction of the individual, the
asexual methods, budding, for example, would have done well enough.
But when it comes to enacting a different individual apart from the
effects of environment, sex stands out as the favored method of Life.

The development of the sexes and the sexual life brought a new element
of conflict into the living world. Before the advent of the sexes the
conflict was essentially for the means of exist