14 SEXUAL SELECTION. Part IL 



" orange-coloured stripes, which give it the appearance 

 " of a Labrus, and the body partakes of a golden-orange 

 " tinge. The females are dark in colour, and are com- 

 " monlv called black-fish."^ An analo":ou3 and even 

 greater change takes place with the Salmo eriox or bull- 

 trout ; the males of the char (S. unibla) are likewise at 

 this season rather brighter in colour than the females.^^ 

 The colours of the pike (Esox reticulatiis) of the United 

 States, especially of the male, become, during the 

 breeding-season, exceedingly intense, brilliant, and iri- 

 descent.^^ Another striking instance out of many is 

 afforded by the male stickleback ( Gasterosteus leiurus), 

 which is described by Mr. Warington,^" as being then 

 " beautiful beyond description." The back and eyes of 

 the female are simply brown, and the belly white. The 

 eyes of the male, on the other hand, are " of the most 

 " splendid green, having a metallic lustre like the 

 " green feathers of some humming-birds. The throat 

 '* and belly are of a bright crimson, the back of an 

 '' ashy-green, and the whole fish appears as though it 

 " were somewhat translucent and glowed with an in- 

 " ternal incandescence." After the breeding-season 

 these colours all change, the throat and belly become 

 of a paler red, the back more green, and the glowing 

 tints subside. 



That with fishes there exists some close relation 

 between their colours and their sexual functions we can 

 clearly see ; — firstly, from the adult males of certain 

 species being differently coloured from the females, and 

 often much more brilliantly ; — secondly, from these same 



20 Yarrell, ' British Fishes,' vol. ii. 1836, p. 10, 12, 35. 



21 W. Thompson, in 'Annals and Mag. of Nat. History,' vol. vi. 1841, 

 p. 440. 



22 « The American Agriculturist,' 1868, p. 100. 



23 ' Annals and Mag. of Nat. Hist.' Oct. 1852. 



