EVOLUTION 1027 



To Groos and to Julian S. Huxley we owe two luminous sug- 

 gestions. In his Play of Animals (Eng. Trans. 1898, p. 242), Groos 

 suggests that " in order to preserve the species the discharge of 

 the sexual function must be rendered difficult, since the impulse 

 to it is so powerful that without some such arrest it might easily 

 become prejudicial to that end". "This very strength of impulse is 

 itself necessary to the preservation of the species; but, on the other 

 hand, dams must be opposed to the impetuous stream, lest the 

 impulse expend itself before it is made effectual, or the mothers of 

 the race be robbed of their strength, to the detriment of their 

 offspring." . . . "The most important factor in maintaining this 

 necessary check is the coyness of the female ; coquetry is the conflict 

 between natural impulse and coyness, and the male's part is to 

 overcome the latter." (Op. cit., p. 243.) 



Not less interesting is the suggestion developed by Julian S. 

 Huxley in his remarkable study of the courtship-habits of the Great 

 Crested Grebe, Podiceps cristatus. {Proc. Zool. Soc. London, 1914, 

 pp. 491-562.) In the Great Crested Grebe the two sexes are practi- 

 cally alike in plumage, colour, and habits; but the courtship is 

 extraordinarily elaborate — a self -exhausting ritual, "not leading 

 up to or connected with coition". Huxley believes that "the court- 

 ship ceremonies serve to keep the two birds of a pair together, and 

 to keep them constant to each other". "Birds have obviously got 

 to a pitch where their psychological states play an important part 

 in their lives. Thus, if a method is to be devised for keeping two 

 birds together, provision will have to be made for an interplay of 

 consciousness or emotion between them." The courtship is justified 

 by the strength of the emotional bond it establishes. There is a 

 "Mutual Selection" which is ia a way "a blend between Sexual and 

 Natural Selection". 



No naturalist has studied a courtship with more thoroughness 

 than Julian Huxley shows in his account of the Great Crested 

 Grebe, and what is his verdict? "Display and ornament do not act 

 on the esthetic sense of the female, but on her emotional state; 

 they are — using the words in no narrow or unpleasant sense — 

 excitants, aphrodisiacs, serving to raise the female into that state 

 of exaltation and emotion when alone she wiU be ready to pair." 

 "... But the element of choice does, in another form, remain. In 

 animals such as Birds, where there is a regular pairing-up season, 

 and where, too, the mental processes are already of considerable 

 complexity, it is impossible to doubt but that mating may be, and 

 in some species is, guided by impulse, unanalysable fancies, indivi- 

 dual predilection." 



A survey of recent observations on mating, such as is afforded 

 by W. P. Pycraft's admirable Courtship of Animals (1913), leaves 

 in the mind a vivid impression of intricacy and subtlety. We agree 



