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 superfiuity 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. 
13%. 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 
