No. 554] ADAPTATION THROUGH SELECTION 71 



breeding in great numbers for many generations from 

 some highly mutating stock. Such work can not well be 

 undertaken by a single individual, for it should continue 

 through several human generations. It should be under- 

 taken by some institution which will ensure the endur- 

 ance of the investigation beyond the present generation. 

 Possibly the best object for such study would be the Syra- 

 cuse Trilliums — Trillium grandifiorum — whose remark- 

 able variation Britcher 3 has so well described. Variation 

 in these Syracuse Trilliums is more universal and more 

 extensive than in any other plants or animals I know. It 

 is so great that it can hardly be of the fluctuating type. 

 It is, in all probability, true mutation, and if so it offers 

 the best opportunity I know for the study of the phenom- 

 ena of mutation. 



Summary 



Organisms show adaptation in their more important 

 characters, while many of their minor characters fail to 

 show their utility. 



There are definite tendencies to mutation in particular 

 directions, and there is abundant paleontological evidence 

 of trends toward increasing modification in particular 

 directions. 



Qualities so appearing may be indifferent in their be- 

 ginnings, but may through this orthogenesis become suffi- 

 ciently useful or hurtful to affect selection. Such trends, 

 when they affect physiological qualities, are likely to 

 bring about an unbalanced, distorted physiological con- 

 dition and be peculiarly hurtful. Probably this has been 

 one of the chief causes of the disappearance of species. 



Orthogenesis as thus interpreted is but the handmaiden 

 of natural selection which, acting upon all qualities thus 

 developed to major proportions, will cause them to disap- 

 pear if ill-adapted. At the same time advantageous 

 trends will be encouraged in the struggle for existence 

 and the direction of evolution be turned toward further 

 adaptation. 



Adaptation is the most salient result of evolution and 

 natural selection its great cause. 



* H. W. Britcher. 



