OR GANIC E } T OL UTION 



Amazon region, Bates says : " It is almost always the males 



only which are beautiful in colors." (See also Plates 31 



and 33, A.} 



The males of many kinds of fishes are more brilliantly 



colored than the females, and in some species the males 



have ornamental ap- 

 pendages which are not 

 found, or are less de- 

 veloped, in the females 

 (Plate 32). Apparently 

 these characters are to 

 be referred to sexual 

 selection, for the colors 



'ff*fjP r * f ~* o 



are generally more 

 brilliant at the breeding 



O 



season, and the behavior 

 of the male in the pres- 

 ence of the female is 

 such as to show off to 

 the best advantage the 



O 



brightly colored parts 

 of his body, or the orna- 

 mental appendages. 

 In some of the An?- 



FK;. 7. Heads of male and female beetles. The 

 left-hand figures show the male. [After DARWIN.] 



A. Copris isidis. B. f'/ian.ciis fan/ins. C. Dipcli- pJllbui the 

 CHS canton. D. Onthophagus rangifer. 



ai'6 



more conspicuous than 

 the females during the breeding season. Darwin says, in 

 his Descent of Jlfaii : "With our common newts (Triton 

 puuctatns and cristatns] a deep, much indented crest is 

 developed along the back and tail of the male during the 

 breeding season, which disappears during the winter (Plate 



