Nos. 622-623] ORGANIC EVOLUTION 



Furthermore, such an idea is more in harmony with the 

 paleontological evidence as presented by Osborn (YM'l) 

 and others, than one based on the mutational idea, and 

 it is to fossil forms that one must look for the all-impor- 

 tant historical record. 



Should one propose a hypothesis of an ultimate unit, 

 slightly plastic as to its immediate environment, but sub- 

 ject to the permutations and combinations of a mendelian 

 type, and possessing a definite qualitative condition de- 

 termined by prolonged environmental action, the picture 

 is not at all so fanciful as some might at first thought 

 insist. 



The practical importance of such a viewpoint in its 

 application to the problems of animal and plant breed- 

 ing lies in the realization that new forms can not be cre- 

 ated, but merely new combinations uncovered during the 

 comparatively brief epochs of time which human intelli- 

 gence has for working out the processes. Thus one re- 

 turns to genetics. 



In summarizing the paper, the following conclusions 

 are suggested: 



I. The heritable characters in general which make up 

 an organism arise from preformed units in the nature of 

 genes or subgenes that have been in existence during long 

 geological periods of time. There are at present no cri- 

 teria available in modern genetics by which an appar- 

 ently new gene may be distinguished from one long in 

 existence ; furthermore, there is doubt as to whether new 

 genes are actually arising in multicellular organisms. 

 The change of a gene in a given direction, whether it be 

 considered as a morphological unit or a chemical condi- 

 tion followed by the return to its original condition, sug- 

 gests its composition of combinational sub-units, and is 

 an argument against the idea that anything- actually new 

 has come into being during its series of so-called muta- 

 tions. Such a conclusion receives additional support 

 from the presence of apparently identical genes which 

 exist in distinct species of organisms separated during 



