The Descent of Man

developed horns by the female reindeer, is due
to the males having first acquired them as weapons
for fighting with other males; and secondarily
to their development from some unknown
cause at an unusually early age in the
males, and their consequent transference to
both sexes.
Turning to the sheath-horned ruminants: with
antelopes a graduated series can be formed,
beginning with species, the females of which
are completely destitute of horns—passing on
to those which have horns so small as to be
almost rudimentary (as with the Antilocapra
americana, in which species they are present in
only one out of four or five females (11. I am
indebted to Dr. Canfield for this information;
see also his paper in the 'Proceedings of the
Zoological Society,' 1866, p. 105.))—to those
which have fairly developed horns, but manifestly
smaller and thinner than in the male and
sometimes of a different shape (12. For instance