VOL. XVI. (1) ORGANIC SELECTION 69 
terms. It must often happen in animal life that fleetness 
makes all the difference between survival and elimination. 
Now there are variations in natural ability; and such 
variations are hereditary. But fleetness is undoubtedly 
improved by individual practice and exercise. There will 
thus be differences in acquired performance due to indivi- 
dually gotten modifications of bodily structure and 
functioning. On the Weismann hypothesis, which we 
have provisionally accepted, these modifications, as such, 
are not hereditary. But may they not indirectly serve to 
determine the survival of like variations? Granting that 
both modifications (M) and variations (V) are either 
positive or negative—above or below the statistical mean 
of fleetness—they may be combined in the following 
ways :— 
a. + V with + M. 
6b. + V with — M. 
c. —-°V with + M. 
= IM. 
as =) Vewith 
It is obvious that the combination d will be eliminated. 
Poor natural ability, combined with poor acquired per- 
formance, will mean failure in the struggle for existence. 
On the other hand, in group a, good natural ability coin- 
cides with good acquired performance. This group will 
comprise the majority of survivors. The favourable 
variations will be inherited; and this because they are 
supported by the coincident favourable modifications. On 
this view, acquired modification is the nurse, not the 
parent, of variation. Such in brief is the hypothesis which 
is termed by Professor Mark Baldwin “ Organic Selection,” 
and which I have described under the more cumbrous 
heading of “ The Survival of Coincident Variations.” The 
idea is that the existence of favourable modifications fosters 
the survival, and therefore the inheritance, of variations of 
like nature. It only remains to be noted that the process 
can only take place under the conditions of natural 
selection. 
