494 ANIMAL LIFE-HISTORIES 



as including the Highest Mammals, if a well-developed brain 

 associated with great intelligence is to be taken as the criterion. 

 The single pair of milk-glands is situated on the chest, and a 

 single young one is the general rule, though an exception is 

 afforded to this by the Marmozets, the lowest members of the 

 order, for in these there is a family of two or three. Parental 

 affection, especially on the part of the mother, is very strongly 

 developed, and necessarily so, for the newly-born young are 

 extremely helpless, and it is a considerable time before they 

 are fully able to look after themselves. One of the most extra- 

 ordinary features in the evolution of human civilization consists 

 in the relatively late age at which maturity is attained, and the 

 large amount of parental sacrifice which this involves. The 

 altruistic attitude to which this has largely contributed is a factor 

 of no small importance in social progress. And it may be added 

 that the study of biology is, or should be, an indispensable pre- 

 liminary for those who interest themselves in the as yet imperfect 

 science of sociology. 



Most Monkeys are arboreal and social in habit, and the 

 immature young are commonly carried about by their mothers, 

 pretty much as in some of the Lemurs. The extraordinary grasp- 

 ing-power of newly-born human infants has been explained as an 

 inheritance from remote tree-living ancestors (see p. 234). Much 

 sagacity is often shown, especially in Old World forms, in the 

 precautions taken for the safety of the community, on similar 

 lines to those adopted by some of the social Ungulates (see 

 p. 365). This is true not only for the arboreal forms but also 

 for the Baboons, which are typical ground-dwellers (see vol. ii, 



P- 363)- 



The highest of the man-like Apes, Orang, Chimpanzee, and 

 Gorilla, do not live in troops, but are associated in family parties. 

 They appear to be in the habit of constructing rough shelters in 

 trees, some 50 or 60 feet from the ground in the case of the 

 Orang, according to Wallace. 



END OF VOL. Ill 



