256 LIFE: ITS NATURE AND ORIGIN 



way as to insure the harmonious co-operation of the parts affected. 

 That neither genetic linkage nor the manifold effects of single 

 genes affords a mechanism for such correlation, to more than a 

 very limited extent, will probably be readily granted. It is prob- 

 able that such an agency, if it exists, must be sought in the field 

 of developmental physiology rather than that of genetics." In 

 physiology catalyst formation and/or modification is a most potent 

 factor, even though not the sole factor. 



We must also remember that what Sumner terms "large steps" 

 have usually taken very long times under unknown conditions, 

 and that our general experimental inability to induce corre- 

 sponding changes by "accelerated" tests done within a few genera- 

 tions, cannot controvert the existing paleontological data. Henry 

 Fairfield Osborn, 18 in summing up the results of over fifty years 

 of study, states: "The evolution of the Titanotheres has little to 

 say about physical or chemical adaptations, but it gives us the most 

 thorough and profound insight we have ever gained into mechan- 

 ical adaptations." Osborn then lists twelve "principles" of adap- 

 tations at the visual or mechanical level of structure, and con- 

 cludes: 



"Whatever may be true as to fortuitous mutation and as to 

 chance or random variation in chemical and physical adaptations, 

 the mechanical evolution of the Titanotheres, a unique record of 

 ten million years in the development of the Titanothere germ- 

 plasm, shows absolute continuity in every single organ examined. 

 There is not the slightest trace of discontinuity or of random 

 origin. There is a firm undeviating orthogenic* order in the entire 

 animal mechanism. There is a phytogenetic continuity of ger- 

 minal adaptation and reaction in response to secular changes of 

 habit and of environment." 



To a book entitled "Creation by Evolution," 19 twenty-six out- 

 standing scientists contributed papers covering many aspects of 

 evolution. The Editor states that the book does not attempt to 

 explain the origin of life, or to determine the causes that lie 

 behind the changes in living things from age to age. It attempts 

 to show that there are changes and to describe how they come 

 about. Though the various authors are unanimous in their dem- 

 onstrations that evolution is a fact, not a single one of them sug- 



* Orthogenesis is denned as "the doctrine that the phylogenetic evolution of 

 organisms takes place systematically in a few definite directions and not accidentally 

 in many directions; determinate variation; a theory of evolution propounded by the 

 German naturalists W. Haacke and T. Eimer" (Standard Dictionary). 



