,

4. An increased or decreased representation of it in the reproductive
sex cells in the gonads.

To take a classic illustration, the long neck of the giraffe. The neck
of certain animals living in a district populated by trees with high
branches would be in state of instability. If at the same time the
pituitary, for some reason, was unstable and reacted with an extra
supply of its secretion, it would stimulate the neck cells to
reproduce themselves. In turn the pituitary would become stabilized
in the direction of increased secretion, and hand on the component of
increased secretion to the sex cells. That component, in conjunction
with other factors, would therefore determine the emergence of a
definite species character. In other words, the glands of internal
secretion, as intermediaries between the environment and body, and
between the body and the reproductive sex cells or germplasm, tender
the clue to a phase of the puzzle of heredity, adaptation and
evolution. It is only a dotted outline of an explanation to be sure,
but one certainly capable of being filled in.

THE BEARING ON BREEDING

Since the endocrine glands are so subtly sensitive and responsive to
environment, and are at the same time so intimately concerned in the
process of inheritance--a law which sums up their influence upon
resemblance and variation in animals--there is no need to stress
their importance for the practical science and art of good breeding,
eugenics. Another mode of approach to its problems is opened up, and
fresh enthusiasm instilled into its hopes and aspirations. A method
of analysis of the factors involved, together with rules for the
prediction of the outcome of certain matings, when finally worked out,
will elevate its procedure to the level of the more exact sciences.

A man's chief gift to his children is his internal secretion
composition. The endocrines are truly the matter of breeding as
they are of growth. They are the material carriers of the inherited
physical and psychic dispositions, powers, abilities and disabilities
from the soma to the germplasm and back from the germplasm to the
soma. All kinds of questions arise as soon as one attempts to consider
the bearing of this underlying principle upon concrete situations.
What happens, say, when a pituitocentric mates with a thyrocentric?
Or when a pituitocentric marries a pituitocentric? Is there a
reinforcement or a cancellation of the dominant endocrine? Is there