When Darwin stated in the first edition of the “Descent of Man,” “as probable that horns of all kinds, even when they are equally developed in the two sexes, were primarily acquired by the male in order to conquer other males, and have been transferred more or less completely to the female,” the “various facts” from which he drew this inference did not include any palæontological evidence. At the present day we are familiar with the notion that, as regards the deer family, the oldest members known, from the Oligocene, were absolutely devoid of antlers, and that the subsequent phylogenetic evolution of the latter has a close parallel in their ontogenetic development.