Instincts, Habits, and Adaptations 155 



ing, those of self-defense and of strife, the instincts of play, the 

 climatic instincts, and environmental instincts, those which direct 

 the animal's mode of life. 



Altruistic instincts are those which relate to parenthood and 

 those which are concerned with the mass of individuals of the 

 same species. The latter may be called the social instincts. 

 In the former class, the instincts of parenthood, may be included 

 the instinct of courtship, reproduction, home-making, nest- 

 building, and care for the young. Most of these are feebly 

 developed among fishes. 



The instincts of feeding are primitively simple, growing com- 

 plex through complex conditions. The fish seizes its prey by 

 direct motion, but the conditions of life modify this simple 

 action to a very great degree. 



The instinct of self-defense is even more varied in its mani- 

 festations. It may show itself either in the impulse to make 

 war on an intruder or in the desire to flee from its enemies. 

 Among carnivorous forms fierceness of demeanor serves at once 

 in attack and in defense. 



Herbivorous fishes, as a rule, make little direct resistance 

 to their enemies, depending rather on swiftness of movement, 

 or in some cases on simple insignificance. To the latter cause 

 the abundance of minnows, anchovies, and other small or feeble 

 fishes may be attributed, for all are the prey of carnivorous 

 fishes, which they far exceed in number. 



The instincts of courtship relate chiefly to the male, the 

 female being more or less passive. Among many fishes the 

 male makes himself conspicuous in the breeding season, spread- 

 ing his fins, intensifying his pigmented colors through mus- 

 cular tension, all this supposedly to attract the attention of the 

 female. That this purpose is actually accomplished by such 

 display is not, however, easily proved. In the little brooks in 

 spring, male minnows can be found with warts on the nose or 

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

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

 bination of all these. Their instinct is to display all these to 

 the best advantage, even though the conspicuous hues lead to 

 their own destruction. 



The movements of many migratory animals are mainly con- 



