less "fit" rivals. A race with thick and solid frontal bones would thus have been established, and it is not difficult to understand how, by the same process of evolution, those portions of the frontal bones which most received the impact of blows, and were most employed to injure rivals, thickened and solidified most (not by the accumulation of acquired variations, but solely by the accumulation of inborn variations, by the survival of the fittest), till there gradually appeared excrescences, which, by the continual survival of the more and more "fit," grew larger in each successive generation, till at last the evolution of horns was completed. That the horns of deer are two in number and symmetrical does not affect the question, for a single horn has been evolved in both the rhinoceros and the narwhale, and in the latter the horn is asymmetrical. Moreover, a fatal objection to Mr. Cunninghame's theory is the fact that horns do not grow under direct stimulation, that of use. It may be that they grow in response to some form of indirect stimulation (sexual emotion), and that they would not develop in an imperfect animal, but I am unable to vouch for this. The essential point is that during growth the horns, being covered by tender "velvet," are carefully protected by the animal from injury, and it is not until the velvet is dead and has peeled away, and growth has ceased, that the animal engages in combat. Use therefore can have had nothing to do with the development of horns.
In the case of worker bees it is impossible that evolution can have proceeded on lines of acquired variations, for the simple reason that since workers have no descendants they cannot transmit any variation acquired or inborn. Their evolution must therefore have resulted from variations in the successive ancestral queens of such a nature as caused them to produce in the course of generations better and better workers; those queens
