HIGHER FUNCTIONS 183 



hand there will be no large families. Tlir i naming 

 Ungulates, ready to flee upon the least ai)i)ic|iiiisi<)ii of 

 danger, have no natural nursery iur tlieir young, and in 

 all of them the family is reduced. The ])elagic (Vtacea 

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



Large families can only be indulged in by animals tliat 

 can have a safe retreat in Avhich to rear their nunu-rous 

 young, or by animals sufficiently equipped witli weapons 

 to guard them. 



Of those animals which, having no nursery to liand, 

 have a reduced litter, there are two distinrt cla.-ses. 

 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 theh^ safety, not upon their retreat into burrows, 

 holes, or any other fastness open to some smaller bea>ts, 

 but upon the swiftness of their open escape. These 

 camiot be successful if the females are handicap])ed by 

 the disabilities of pregnancy with large litters, or by the 

 nursing of helpless offspring. In them the number A 

 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 tlie 

 arboreal animals. There is no natural nursery anion^; 

 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-buildinu wa-- 

 resorted to as a temporary expedient in the ari)oreal 

 stock; and among all the arboreal and semi-ar])oreal 

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

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



