[25] It is scarcely necessary to point out that this is too extreme a position.  As J.G.  Millais remarks of ducks (Natural History of British Ducks, p. 45), in courtship “success in winning the admiration of the female is rather a matter of persistent and active attention than physical force,” though the males occasionally fight over the female.  The ruff (Machetes pugnax) is a pugnacious bird, as his name indicates.  Yet, the reeve, the female of this species, is, as E. Selous shows ("Sexual Selection in Birds,” Zooelogist, Feb. and May, 1907), completely mistress of the situation.  “She seems the plain and unconcerned little mistress of a numerous and handsome seraglio, each member of which, however he flounce and bounce, can only wait to be chosen.”  Any fighting among the males is only incidental and is not a factor in selection.  Moreover, as R. Mueller points out (loc. cit., p. 290), fighting would not usually attain the end desired, for if the males expend their time and strength in a serious combat they merely afford a third less pugnacious male a better opportunity of running off with the prize.

[26] L. Tillier, L’Instinct Sexuel, 1889, pp. 74, 118, 119, 124 et seq., 289.

[27] K. Groos, Die Spiele der Thiere, 1896; Die Spiele der Menschen, 1899; both are translated into English.

[28] Prof.  H.E.  Ziegler, in a private letter to Professor Groos, Spiele der Thiere, p. 202.

[29] Die Spiele der Thiere, p. 244.  This had been briefly pointed out by earlier writers.  Thus, Haeckel (Gen. Morph., ii, p. 244) remarked that fighting for females is a special or modified kind of struggle for existence, and that it acts on both sexes.

[30] It may be added that in the human species, as Bray remarks ("Le Beau dans la Nature,” Revue Philosophique, October, 1901, p. 403), “the hymen would seem to tend to the same end, as if nature had wished to reinforce by a natural obstacle the moral restraint of modesty, so that only the vigorous male could insure his reproduction.”  There can be no doubt that among many animals pairing is delayed so far as possible until maturity is reached.  “It is a strict rule amongst birds,” remarks J.G.  Millais (op. cit., p. 46), “that they do not breed until both sexes have attained the perfect adult plumage.”  Until that happens, it seems probable, the conditions for sexual excitation are not fully established.  We know little, says Howard (Zooelogist, 1903, p. 407), of the age at which birds begin to breed, but it is known that “there are yearly great numbers of individuals who do not breed, and the evidence seems to show that such individuals are immature.”

[31] A. Marro, La Puberte, 1901, p. 464.

[32] Lloyd Morgan, Animal Behavior, 1900, pp. 264-5.  It may be added that, on the esthetic side, Hirn, in his study (The Origins of Art, 1900), reaches conclusions which likewise, in the main, concord with those of Groos.