ADAPTATION FOR THE INDIVIDUAL 105 
ture has concocted many devices by which she assists 
her favored children in escaping this relentless perse- 
cution. Perhaps the most widespread means which 
animals have developed in order to elude their ene- 
mies lies in the possession of power to escape their 
attention. Two different factors may contribute to 
this end. The first of these consists in the practice on 
the part of many animals of remaining absolutely 
quiet in time of danger. This instinct seems to be 
nearly universal. The first impulse of most animals 
upon discovering danger is to remain absolutely mo- 
tionless. The eye detects, with ease, objects in mo- 
tion. These same objects might entirely escape atten- 
tion were they quiet. A mouse could remain in the 
corner of a room for a long time without attracting 
the eyes of the occupants of the room. Let it but 
scamper across the corner, and at once it is discov- 
ered. It is quite conceivable that early animals were 
divided in the matter; that the impulse of some was to 
escape from danger, while others, frightened by the 
presence of the enemy, remained absolutely still. Each 
plan has succeeded. Those which, on running, ran 
fast enough to escape became the parents of others 
like themselves, led eventually to a line of animals in 
whose speed lay their safety. Those, however, which 
attempted to escape, and failed because they were not 
swift enough, had their line cut off, and were thus 
