HIGHER FUNCTIONS 183 



hand there will be no large families. The roaming 

 Ungulates, ready to flee upon the least apprehension of 

 dangerTTTave no natural nursery for their young, and in 

 all of them the family is reduced. The pelagic Cetacea 

 are in the same condition, and so also are the Sirenia. 



Large families can only be indulged in by animals that 

 can have a safe retreat in which to rear their numerous 

 young, or by animals sufficiently equipped with weapons 

 to guard them. 



Of those animals which, having no nursery to hand, 

 have a reduced litter, there are two distinct classes. 

 The first class, for which we may turn to the horse (as 

 a representative of the Ungulates) for an example, is 

 made up of animals whose roaming life is composed of 

 a series of escapes from danger; animals that depend 

 for their safety, not upon their retreat into burrows, 

 holes, or any other fastness open to some smaller beasts, 

 but upon the swiftness of their open escape. These 

 cannot be successful if the females are handicapped by 

 the disabilities of pregnancy with large litters, or by the 

 nursing of helpless offspring. In them the number of 

 offspring is reduced, and the usually solitary infant is 

 born singularly mature, so that it may share as soon as 

 possible in the life-saving activities of its species. 



The solitary young of such animals is born " grown 

 up," it can flee at its mother's side within a few hours of 

 its birth. Its period of dependence upon its mother is 

 relatively short, and there is but little infancy, or child- 

 hood, for such a baby. In the second class come the 

 arboreal animals. There is no natural nursery among 

 the tree-tops, and the disabilities of pregnancy with a 

 large litter are felt as keenly in active tree-climbers as 

 in any class of animals. No doubt nest-building wa? 

 resorted to as a temporary expedient in the arboreal 

 stock; and among all the arboreal and semi-arboreal 

 animals derived from many orders, nest-building, in some 

 members, is^ still the rule. But nest-building only over- 



