io ANIMALS AT WORK AND PL A Y 



There is good reason to believe that the broken 

 and timid form of animal sleep in the greater 

 number of species, is not such as they would 

 naturally choose, but is the result of habits acquired 

 and transmitted in centuries of danger and avoid- 

 ance of their enemies ; and that the same causes 

 which have modified the hours of sleep, have also 

 modified its character. Of the animals which, when 

 wild, now sleep by day, snatching broken periods 

 of unrestful slumber as and where they can, not a 

 twentieth part are night-feeders by nature or choice. 

 The true nocturnal animals are those which can only 

 find their food at night. With the exception of the 

 owls and opossums, which are only partly insectiv- 

 orous, they are nearly all insect-eaters, bats, lemurs, 

 lorises and nightjars ; and though the last, like the 

 owls, do move with rapidity and some precision 

 when once disturbed, the others might be dis- 

 tinguished from those creatures which are only 

 nocturnal by necessity, by the absence of that wake- 

 fulness in sleep which the latter possess in such a 

 marked degree. The bats, lemurs and lorises are, 

 during the day, steeped and drugged with slumber. 

 If once discovered, they make no effort to escape ; 

 like the opossums, which let the ' black fellows ' 

 c.hop them out of their holes in the hollow trees 

 without moving from their sleeping-places, it does 



