INSTINCT AND REASON 249 



with crimson pigment on the fins, or blue pigment on the 

 back, or jet-black pigment all over the head, or with varied 

 combinations of all these. Their instinct is to display all 

 these to the best advantage, even though the conspicuous 

 hues lead to their own destruction. Against this contin- 

 gency Nature provides a superfluity of males. 



Among the birds the male in spring is in very many 

 species provided with an ornamental plumage which he 

 sheds when the breeding season is over. The scarlet, crim- 

 son, orange, blue, black, and lustrous colors of birds are 

 commonly seen only on the males in the breeding season, 

 the young males and all males in the fall having the plain 

 brown gray or streaky colors of the female. Among the 

 singing birds it is chiefly the male that sings, and his voice 

 and the instinct to use it are commonly lost when the young 

 are hatched in the nest. 



Among polygamous mammals the male is usually much 

 larger than the female, and his courtship is often a 

 struggle with other males for the possession of the female. 

 Among the deer the male, armed with great horns, fight 

 to the death for the possession of the female or for the 

 mastery of the herd. The fur-seal has on an average a 

 family of about thirty-two females (Fig. 71), and for the 

 control of his harem others are ready at all times to dispute 

 the possession. But with monogamous animals like the 

 true or hair seal or the fox, where a male mates with a 

 single female, there is no such discrepancy in size and 

 strength, and the warlike force of the male is spent on out- 

 side enemies, not on his own species. 



137. Reproduction. The movements of many migra- 

 tory animals are mainly controlled by the impulse to repro- 

 duce. Some pelagic fishes, especially flying-fishes and fishes 

 allied to the mackerel, swim long distances to a region 

 favorable for a deposition of spawn. Some species are 

 known only in the waters they make their breeding homes, 

 the individuals being scattered through the wide seas at 



