PREFACE xiii 



Cope turned from the form of the teeth and skeleton backward 

 to considerations of cause and energy, Osborn^ reached a con- 

 ception of evolution as of the relations of fourfold form, and 

 hence proposed the word tetraplasy. 



The Heredity theories of Darwin, of de Vries, of Weis- 

 mann have also been largely in the material conceptions of 

 fine particles of matter such as "pangens" and "determinants." 

 There has been some consideration of function and of the 

 internal phenomena of organisms, but there has been little 

 or no serious attempt to reverse the mental processes of the 

 naturalist and substitute those of the physicist in considering 

 the causes of evolution. - 



Moreover, all the explanations of evolution which have 

 been offered by three generations of naturalists align themselves 

 under two main ideas only. The first is the idea that the 

 causes of evolution are chiefly from without inward, namely, 

 beginning in the environment of the body and extending into 

 the germ: this idea is centripetal. The second idea is just the 

 reverse: it is centrifugal, namely, that the causes begin in the 

 germ and extend outward into the body and into the environ- 

 ment. 



The pioneer of the first order of ideas is Buff on, who early 

 reached the opinion that favorable or unfavorable changes 

 of environment directly alter the hereditary form of succeed- 

 ing generations. Lamarck,^ the founder of a broader and 

 more modern conception of evolution, concluded that the 

 changes of form and function in the body and nervous system 

 induced by habit and environment accumulate in the germ, 



' Osborn, H. F., "Tetraplasy, the Law of the Four Inseparable Factors of Evolution," 

 Jour. Acad. Nat. Sci. Pliila., special anniversary volume issued September 14, 1912, pp. 

 275-309- 



^ See fuller exposition on pp. 10-23 of this volume. 



' For a fuller exposition of the theory of Lamarck, see pp. 143, 144. 



