1880.] A Review of the Modern Doctrine of Evolution. 175 
vation necessarily survive, while the weak in resources must dis- 
appear from the scene. Hence those which survive must dis- 
play some especial fitness for existence under the circumstances 
of their environment, whatever they may be. So the “ survival 
of the fittest ” is believed to be a law of evolution, and the pro-« 
cess by which it is brought about has been termed “natural selec- 
tion.” The works of Darwin and others have satisfied biologists 
that this is a vera causa. 
Before the excellence of a machine can be tested, it must exist, 
and before man or nature selects the best, there must be at least two 
to choose from as alternatives. Furthermore it is exceedingly im- 
probable that the nicely adapted machinery of animals should have 
come into existence without the operation of causes leading 
directly to that end. The doctrines of “ selection” and “survival” 
plainly do not reach the kernel of evolution, which is, as I have 
long since pointed out, the question of ‘‘the origin of the fittest.” 
The omission of this problem from the discussion of evolution, 
is to leave Hamlet out of the play to which he has given the 
name, The law by which structures originate is one thing; those 
by which they are restricted, directed, or destroyed, is another 
thing. 
There are two kinds of evolution, progressive and retrogres- 
sive ; or, to use expressions more free from objection, by ad- 
dition of parts, and by substraction of parts. It is further 
evident that that animal which adds something to its struc- 
ture which its parents did not possess, has grown more than , 
they; while that which does not attain to all the characteristics 
of its ancestors has grown less than they. To express the change 
in the growth-history which constitutes the beginning of evo- 
lution, I have employed the terms “ acceleration and retardation.” 
Generally these expressions are literally exact, £. e., there is an in- 
creased rate of growth in evolution by addition, and a decreased 
rate in evolution by subtraction; but this is not always the case, — 
for some divisions of animals have increased the léngth of their 
Srowth-period without reference to evolution in structure. The 
terms express the phenomena figuratively, where not exact in the 
sense of time, and I believe they are sufficiently clear. The or igin 
of the fittest is then a result of either acceleration or retardation. 
It 1S easy to perceive that a character which makes its appearance 
1n a parent before or near to the breeding season wel whe o 
