Instincts, Habits, and Adaptations 41 
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- 
