SEXUAL SELECTION 443 



rather brighter in color than the females." The colors of 

 the pike {Esox recUculatus) of the United States, especially 

 oi the male, become, during the breeding season, exceed- 

 ingly intense, brilliant, and iridescent." Another striking 

 instance out of many is afforded by the male stickleback 

 {Gasterosteus leiurus), which is described by Mr. Waring- 

 ton" 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 internal incandescence." After the 

 breeding season these colors all change, the throat and belly 

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

 tints subside. 



With respect to the courtship of fishes, other cases have 

 been observed, since the first edition of this book appeared, 

 besides that already given of the stickleback. Mr. W. S. 

 Kent says that the male of the Ldbrus mixtus, which, as we 

 have seen, differs in color from the female, makes "a deep 

 hollow in the sand of the tank, and then endeavors, in the 

 most persuasive manner, to induce a female of the same 

 species to share it with him, swimming backward and for- 

 ward between her and the completed nest, and plainly ex- 

 hibiting the greatest anxiety for her to follow." The malea 

 of Cantharus lineatus become, during the breeding season, of 

 deep leaden black; they then retire from the shoal, and ex- 

 cavate a hollow as a nest. "Each male now mounts vigilant 

 guard over his respective hollow, and vigorously attacks and 

 drives away any other fish of the same sex. Toward his 

 companions of the opposite sex his conduct is far different; 



S3 "W. Thompson, in "Annals and Mag. of Nat. History," vol. vl, \%4X, 

 p. 440. 



" "The American Agriculturist," 1868, p. 100. 

 »6 "Annals and Mag. of ITat. Hist.," Oct. 1852. 



