12 PREFACE 



can be perf ectly harmonized with the paleontological record there 

 is, to the writer's mind, no reason for further hesitation in 

 accepting as a fundamental basis of mammalian tooth forms 

 the Cope-Osborn theory clothed in its most modern guise. All 

 other interpretations have been made subservient to this and 

 the reader's mind is not distracted by reference either fre- 

 quently or fully to other views. 



It has been the intention of the writer to illustrate three 

 fundamental principles of life: the marvellous potentiality for 

 adaptation exhibited by organisms in general through the con- 

 tinual creation of the absolutely new; the occurrence of adapta- 

 tions always in one of several definite directions; the frequency 

 of pause, reversal, or secondary progression, in other words the 

 discontinuous character of evolution. 



In every field it has been human fortune to discover first the 

 laws of blood and iron, to gain an impression of irrevocable 

 immutable implacable pitiless Force unsoftened'by one touch 

 of tenderness. Only with the fuller biological knowledge comes 

 the vision that "if the courses be departed from, the ends 

 will change" and further that the courses can be and con- 

 stantly are departed from. One recollects hoAV Claude Ber- 

 nard's spirit revolted from the views current forty years 

 ago when he wrote: "It is not by struggling against cosmic 

 conditions that the organism develops and maintains its place ; 

 on the contrary, it is by an adaptation to, an agreement with 

 these conditions. So the living being does not form an excep- 

 tion to the great natural harmony which makes things adapt 

 themselves to one another; it breaks no concord; it is neither 

 in contradiction to nor struggling against general cosmic 

 forces; far from that, it forms a member of the universal 

 concert of things, and the life of the animal, for exam- 

 ple, is only a fragment of the total life of the universe." 

 At this time when the soul of France typifies the spirit of 

 emancipation from all that is hide-bound and cruelly inexora- 

 ble, it is delightful to remember that Bernard's fellow-coun- 



