Darwin's Artificial and Natural Selection 107 
to another may be safely attributed to the cumulative action 
of natural selection, hereafter to be explained, and to the 
effects of the increased use or disuse of parts. A well- 
marked variety may therefore be called an incipient species ; 
but whether this belief is justifiable must be judged by the 
weight of the various facts and considerations to be given 
throughout this work.” 
In this paragraph attention should be called especially, 
first, to the statement in respect to the origin of varieties, 
which are said to arise through individual differences. It 
is not clear whether these differences are supposed to have 
appeared first in one, or in a few individuals, or in large 
numbers at the same time. Again, especial note should 
be made of the striking admission, that the passage from 
one stage to another may, in many cases, be the simple 
result of the nature of the organism and of the physical 
conditions surrounding it; but with respect to the more 
important and adaptive differences, natural selection “may 
safely” be supposed to have intervened. Is it to be won- 
dered at that Darwin’s critics have sometimes accused him 
of playing fast and loose with the origin of varieties? And 
since this question is fundamental for the theory of natural 
selection, it is much to be regretted that Darwin leaves the 
matter in such a hazy condition. It may be said that, at 
the time when he wrote, he made the best of the evidence 
in regard to the origin of varieties. Be this as it may, a 
theory standing on no better foundations than this is not 
likely to be found satisfactory at the present time. 
We come now to the most important chapters, the third 
and the fourth, of the “ Origin of Species,” dealing with “ the 
struggle for existence,” “ natural selection,” or the “survival 
of the fittest.” Behind these fatal phrases, which have become 
almost household words, lurk many dangers for the unwary. 
“Tt has been seen in the last chapter that amongst organic 
beings in a state of nature there is some individual variability : 
