1896.] A New Factor in Evolution. 551 
or that it is a fundamental endowment of life and part of its 
final mystery. “ The intelligence holds a remarkable place. 
It is itself, as we have seen, a congenital variation; but it 1s 
also the great agent of the individual’s personal adaptation 
both to the physical and to the social environment ” (ref. 4). 
“ The former (instinct) represents a tendency to brain varia- 
tion in the direction of fixed connections between certain sense- 
centers and certain groups of codrdinated muscles. This 
tendency is embodied in the white matter and the lower brain 
centers. The other (intelligence) represents a tendency to varia- 
tion in the direction of alternative possibilities of connection 
of the brain centers with the same or similar codrdinated 
muscular groups. This tendency is embodied in the cortex of 
the hemispheres ” (ref. 4). 
2. But however that may be, whether ontogenetic adaptation 
by selective reaction and consciousness be considered a varia- 
tion or a final aspect of life, it is a life-qualification of a very 
extraordinary kind. It opens anew sphere for the application of 
the negative principle of natural selection upon organisms, i. e., 
with reference to what they can do, rather than to what they 
are; to the new use they make of their congenital functions, 
rather than to the mere possession of the functions (ref. 2, pp. 
202 f.). A premium is set on congenital plasticity and adapta- 
bility of function rather than on congenital fixity of function; 
and this adaptability reaches its highest in the intelligence. 
3. It opens another field also for the operation of natural 
selection—still viewed as a negative principle—through the 
survival of particular overproduced and modified reactions of 
the organism, by which the determination of the organism’s 
own growth and life-history is secured. Ifthe young chick 
imitated the old duck instead of the old hen, it would perish ; 
it can only learn those new things which its present equip- 
ment will permit—notswimming. So the chick’s own possible 
actions and adaptations in ontogeny have to be selected. We 
have seen how it may be done by a certain competition of 
functions with survival of the fit. But this is an application 
of natural selection. I do not see how Henslow, for example, 
can get the so-called “self-adaptations”—apart from “ special 
