SEXUAL SELECTION 159 



Linnaeus considered the dingy reddish-brown female the repre- 

 sentative of a different species. 1 



Among amphibians there are sometimes colour differences 

 between the sexes, e.g. in the newts. But the most striking 

 sexual distinction is the great development of the vocal organs 

 among frogs and toads. In Teneriffe the chorus of the green 

 tree-frogs makes evening hideous. But with all this noise, there 

 seems to be no fighting. 



Among reptiles we find not only varieties of crests and pouches 

 peculiar to the stronger sex, but battles between rival males. 

 The huge male tortoise of the Galapagos Islands utters a 

 "bellowing noise" in the pairing season, which, however, does 

 not seem to be very loud. Male alligators have been seen 

 splashing and roaring in an ostentatious way round a female, 

 but it is apparently unknown whether they fight with one 

 another. However, some kinds of lizards are undoubtedly 

 pugnacious. Two adult males of Anolls cristatellus, a South 

 American arboreal species, " rarely met without a contest." 2 



There has been a boom in birds lately that ought to have 

 made the main facts familiar, so that only a very brief review 

 of them should be necessary. Their battles everyone knows of; 

 the noisy scrimmages of house sparrows, the tragic encounters 

 of game cocks, the stately sparrings of ruffs {Machetes pugtiax) 

 that are said, however incredibly, to end like Pickwickian 

 quarrels in nobody being any the worse. Feathers are 

 admirably adapted for colour display. The most beautiful 

 colours of all, the iridescent, are produced without the aid 

 of any pigment and cannot be said to tax in any way the bird's 

 fund of vitality. But in such birds as the argus pheasant 

 and the bird of paradise the ornamental plumes are of such 

 dimensions as to impede flight, to say nothing of the strain that 

 the annual production of them must put upon the vital re- 

 sources. In many species song takes the place of colour, and 

 it is seldom that we find both highly developed in the same 



1 Figures of very brilliantly coloured fish of the Plectognathi group are given in 

 Mr Savile Kent's Naturalist in Australia. 



2 Quoted by Darwin, Descent of Man, vol. ii. p. 32. 



