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, ete.) 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 
VOL. I. Q 
