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Biology in America 



The result is not death to the unsuccessful competitor, but 

 few or no offspring. . . . Generally, the most vigorous males, 

 those which are best fitted for their places in nature, will 

 leave most progeny. But in many cases, victory depends not 

 so much on general vigor, as on having special weapons, con- 

 fined to the male sex. A hornless stag or spurless cock would 

 have a poor chance of leaving numerous offspring. Sexual 

 selection, by always allowing the victor to breed, might surely 

 give indomitable courage, length to the spur, and strength 



MALE AND FEMALE WOOD DUCKS 



Showing sexual differences in color, from an illustration by Louis 

 Agassiz Fuertes. 



Courtesy of the U. S. Bureau of Biological Survey. 



to the wing to strike in the spurred leg, in nearly the same 

 manner as does the brutal cockfighter by the careful selection 

 of his best cocks. How low in the scale of nature the law 

 of battle descends, I know not; male alligators have been 

 described as fighting, bellowing, and whirling around, like 

 Indians in a war-dance, for the possession of the females; 

 male salmons have been observed fighting all day long; male 

 stag-beetles sometimes bear wounds from the huge mandibles 

 of other males; the males of certain hymenopterous insects 

 have been frequently seen by that inimitable observer M. 

 Fabre, fighting for a particular female who sits by, an ap- 



