ration of disused parts cannot be over-estimated, especially when
it occurs in sterile animal forms, where we are free from the doubt as
to the alleged LAMARCKIAN FACTOR which is apt to confuse our ideas in
regard to other cases.

If we regard the variation of the many determinants concerned in the
transformation of the female into the sterile worker as having come
about through the gradual transformation of the ids into worker-ids,
we shall see that the germ-plasm of the sexual ants must contain three
kinds of ids, male, female, and worker ids, or if the workers have
diverged into soldiers and nest-builders, then four kinds. We understand
that the worker-ids arose because their determinants struck out a useful
path of variation, whether upward or downward, and that they continued
in this path until the highest attainable degree of utility of the parts
determined was reached. But in addition to the organs of positive or
negative selection-value, there were some which were indifferent as far
as the success and especially the functional capacity of the workers was
concerned: wings, ovarian tubes, receptaculum seminis, a number of the
facets of the eye, perhaps even the whole eye. As to the ovarian tubes
it is possible that their degeneration was an advantage for the workers,
in saving energy, and if so selection would favour the degeneration; but
how could the presence of eyes diminish the usefulness of the workers to
the colony? or the minute receptaculum seminis, or even the wings? These
parts have therefore degenerated BECAUSE THEY WERE OF NO FURTHER VALUE
TO THE INSECT. But if selection did not influence the setting aside of
these parts because they were neither of advantage nor of disadvantage
to the species, then the Darwinian factor of selection is here
confronted with a puzzle which it cannot solve alone, but which at once
becomes clear when germinal selection is added. For the determinants
of organs that have no further value for the organism, must, as we have
already explained, embark on a gradual course of retrograde development.

In ants the degeneration has gone so far that there are no
wing-rudiments present in ANY species, as is the case with so many
butterflies, flies, and locusts, but in the larvae the imaginal discs of
the wings are still laid down. With regard to the ovaries, degeneration
has reached different levels in different species of ants, as has been
shown by the researches of my former pupil, E