CHAPTER VIII 

 EVOLUTION OF THE MAMMALS 



First mammals, of insectivorous and tree-living habits. Single character 

 evolution, physicochemical interaction, coordination, and complexity. 

 Problem as to the causes of the origin of new characters and of new 

 bodily proportions. Adaptations of the teeth and of the limbs as observed 

 in direct, reversed, alternate, and counteracting evolution. Physiographic 

 and climatic environment during the period of mammalian evolution, in a 

 measure deduced from adaptive variations in teeth and feet of mammals. 

 Conclusions, present knowledge of biologic evolution among the verte- 

 brate animals. Future lines of inquiry into the causes of evolution. 



It required a man of genius like Linnaeus to conceive the 

 inclusion within the single class Mammalia of such diverse 



TK,. 111. 1 Ui. blA W'iiALL, LiAL.L;.ui'il.i:.v Imjrlali.--, 



Which attains a total length of forty-nine feet. Restoration (upper) and photograph 



(lower) after Andrews. 



forms as the tiny insect-loving shrew and the gigantic preda- 

 ceous whale. It has required one hundred and twenty-five 

 years of continuous exploration and research to establish the 

 fact that the whale type (Fig. iii), is not only akin to but 



234 



