426 KA BATHAER [DECEMBER 
through selection will be proportional to the number of variations in 
the direction of progress. If variations be governed by the laws of 
chance alone, that number must be less than when variations are 
determined in the direction of the environment by the inheritance of 
modification. Fitness would be reached more readily if modifications 
were inherited. 
The second consideration is more subtle. It is a question whether 
education or the action of the external world can add anything to the 
nature of the organism, whether it does not merely unfold and develop 
the original nature. Here is the old difference between development 
by epigenesis and by evolution. Dr. Brooks makes a compromise 
that seems consistent with common sense. The organism, he says, 
would not develop without the education, but the character of the 
development is due to its original nature (p. 15). No vital action 
takes place without a stimulus; but the stimulus is one thing, the 
character of the action is another, and is dependent on the nature of 
the organism. Thus in ontogeny each change may be called forth by 
some mechanical stimulus, either within the body or without, and yet 
the nature of the whole may depend on the nature of the germ 
(p. 59). “External conditions press the button, but it takes all the 
inherent potency of living matter to do the rest” (p. 61). 
An ingenious application of this conception may be noted in pass- 
ing. It is that “organs once adjusted to the external world may, 
after the adjustment has lost its meaning, be still retained, because 
they furnish physiological stimuli, which excite developmental 
changes in the organic mechanism” (p. 10). Thus Dr. Brooks 
accounts for the retention of so-called rudimentary organs and recapitu- 
latory stages. 
But we have to see how the conception affects the problem of 
fitness. If it be correct, if, in other words, nurture adds nothing to 
nature, then there is nothing to be inherited. But the problem does 
not become easier of solution. It consists of two parts: the adapta- 
bility of the individual; and the adaptation of the race. The adapta- 
bility of the individual resolves itself into the adaptability of 
protoplasm, and none is so bold as to say he knows the explan- 
ation of this. Turning to the adaptation of the race; each new 
germ would, on this conception, be similar in all respects to the 
primordial protoplasm, being in fact nothing but an extended part 
thereof, but gradually becoming more and more gifted with the power 
of growing into a being modified in accordance with its environment. 
But it is very difficult to see why or how it should obtain this power, 
except through education. The faculty of being educated was, we 
may suppose, present in the original protoplasm; and it has gone on 
being educated ever since. Some portions of it, from one cause or 
another, did not respond so readily to education, and they have been 
expelled in consequence; that is what we mean by natural selection. 

