262 The Unity of the Organism 



cially critical experimental era. I quote from his well- 

 known The Naturalist in La Plata, published in 1892: "I 

 wish now to put this question : What relation that we can 

 see or imagine to the passion of love and the business of 

 courtship have these dancing and vocal performances in 

 nine cases out of ten? In such cases, for instance, as that 

 of the scissor-tail tyrant-bird, and its pyrotechnic evening 

 displays, when a number of couples leave their nests, con- 

 taining eggs and young, to join in a wild aerial dance; the 

 mad exhibitions of ypecahas and ibises, and the jacanas' 

 beautiful display of grouped wings ; the triplet dances of 

 the spur-winged lapwing, to perform which two birds already 

 mated are compelled to call in a third to complete the set; 

 the harmonious duets of the oven-birds, and the duets and 

 choruses of nearly all the wood-hewers, and the wing-slap- 

 ping aerial displays of the whistling widgeons ; will it be 

 seriously contended that the female of this species makes 

 choice of the male able to administer the most vigorous and 

 artistic slaps? . . . There are many species in which the 

 male, singly or with others, practises antics or sings during 

 the love-season before the female; and when all such cases, 

 or rather those which are most striking and bizarre, are 

 brought together, and when it is gratuitously asserted that 

 the females do choose the males that show off in the best 

 manner or that sing best, a case for sexual selection seems 

 to be made out. How unfair the argument is, based on these 

 carefully selected cases gathered from all regions of the 

 globe, and often not properly reported, is seen when we turn 

 from the book to Nature, and closely consider the habits and 

 actions of all the species inhabiting any one district. We 

 see then that such cases as those described and made so much 

 of in the 'Descent of Man,' and cases like those mentioned 

 in this chapter, are not essentially different in character, 

 but are manifestations of one instinct, which appears to be 

 almost universal among the higher animals. The explana- 



