DIRECT AND INDIRECT ADAPTATION. 225 



As this very important and very general phenomenon had 

 hitherto been entirely neglected, people were inclined to 

 consider all the visible variations and transformations of 

 organic forms as phenomena of adaptation of the second 

 series, that is, as phenomena of direct or actual adaptation. 

 The essence of this latter kind of adaptation consists in the 

 fact that the change affecting the organism (through nutri- 

 tion, etc.) shows itself immediately by some transformation, 

 and does not only make itself apparent in the descend- 

 ants. To this class belong all the well-known phenomena 

 in which we can directly trace the transforming influence of 

 climate, food, education, training, etc., in their effects upon 

 the individual itself. 



We have seen how the two series of phenomena of pro- 

 gressive and conservative transmission, in spite of their 

 difference in principle, in many ways interfere with and 

 modify each other, and in many ways co-operate with and 

 cross each other. The same is the case, in a still higher 

 degree, in the two series of phenomena of indirect and 

 direct adaptation, which are opposed to each other and yet 

 closely connected. Some naturalists, especially Darwin and 

 Carl Vogt, ascribe to the indirect or potential adaptation 

 by far the more important and almost exclusive influence. 

 But the majority of naturalists have hitherto been inclined 

 to take the opposite view, and to attribute the principal 

 influence to direct or actual adaptation. I consider this 

 controversy, in the mean while, as almost useless. It is but 

 seldom that we are in a condition, in any individual case of 

 variation, to judge how much of it belongs to direct and 

 how much to indirect adaptation. We are, on the whole, 

 still too little acquainted with these exceedingly important 



