274 DARWINISM TO-DAY. 



of the inheritance of acquired characters in some degree or 

 under certain conditions and this partial acceptance has 

 always seemed to me no more justified than the flat accept- 

 ance of the principle in its entirety ; it has seemed a weak 

 sort of attempt at compromise with no real basis in reason 

 and effecting no advantage in clearing up the problem 

 there can be no acceptance of the all-sufficiency of Lamarck- 

 ism as an explanation of adaptation, species-forming, and 

 descent, any more than there can be such an acceptance of 

 the all-sufficiency of natural selection. Adaptation and spe- 

 cies-forming are not, to my mind, one and the same problem : 

 adaptation can and does lead to species-forming, but species 

 are formed that are not the results of adaptive modifica- 

 tion ; whose specific characteristics are indifferent ; that are, 

 in a word, non-adaptive species. De Vries's new species of 

 evening primroses have a cause not associated with adapta- 

 tion. Now Lamarckism certainly cannot explain non- 

 adaptive species any better than selection can. Both selec- 

 tion and the inheritance of the effects of use, disuse, and 

 external stimuli are primarily explanations of adaptations- 

 and of adaptive species-forming. Lamarckism is, perhaps, 

 through its inclusion of the perpetuation of the direct influ- 

 ence of external stimuli, in better condition to explain non- 

 adaptive species, but both of these genius-offered explana- 

 tions of organic evolution need the aid of another or other 

 factors : the unknown factors of evolution, to speak with 

 Osborn. 



Orthogenesis. One of the principal criticisms of the 

 natural selection theory is that of the impossibility of ex- 

 plaining the beginnings of advantageous modi- 



-cippB.r6nti 6V1* 



dence for ortho- fication and the beginnings of new organs, by 

 genetic evolution, the selection of fluctuating individual variation, 



and of explaining the apparent cases of the existence of 

 determinate variation and the admitted cases of forthright 

 development along fixed lines not apparently advantageous,. 



