6o 



GENERAL PRINCIPLES OF ZOOLOGY. 



phase of natural selection, which has chiefly been observed 

 in the case of birds and hoofed animals. For the fulfil- 

 ment of his sexual instincts the male seeks to drive his 

 competitors from the field, either in battle or by impress- 



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FIG. i^.\.~Paradisea apoda, male. (After Levaillant.) 



ing the female by his special excellences. With strong 

 wings and with spurs the cock maintains possession of his 

 flock, the stag by means of his antlers, the bull with his 

 horns; the birds of paradise by means of beautiful color- 

 ing win the favor of the females, most singing birds by 

 means of their song, many species of the fowl tribe by 



