10 
mere variations [in which mere individual differences are 
included] that it is impossible to separate them. 
Mr. Wallace says that variation is generally very small 
in amount ; that variation is merely the absence of 
identity : and yet he also says few persons consider how 
largely and universally all animals are varying. 
A similar difference of opinion is found as to whether 
the same variation will occur in one or a few, or in many 
individuals. 
Mr. Darwin says: “These individual differences afford 
materials for Natural Selection to act on.”—(Origin of 
Species. p. jp) 
Professor Huxley says: “ The variations from their 
specific type which individuals present ‘ are the objects of’ 
the selective action of external conditions.” 
Mr. Romanes says :— 
“The theory of Natural Selection, as such, furnishes no warrant 
for supposing that the same beneficial variety should arise in a 
number of individuals spontaneously. On the contrary, the theory of 
Natural Selection trusts to the chapter of accidents in the matter of 
variation ; and in this chapter we read of no reasons why the same 
beneficial variation should arise simultaneously in a sufficient number 
of individual cases to prevent its being swamped by intercrossing 
with the parent species.” 
Hence it is contended that— 
“ A very large assumption is made, when it is said that the same 
variation occurs simultaneously in a number of individuals inhabiting 
the same area.”—{The Journal of the Linnean Society, vol. xix., 
Zoology, p. 34J.) 
To this, Mr. Wallace, speaking from actual observation 
of nature, makes the following reply:— 
“ But that which Mr. Romanes regards as ‘ a very large assumption,’ 
is, I maintain, a very general fact, and at the present time, one of the 
best established facts in natural history. A brief summary of these 
facts is given in my ‘ Island Life’ (p. 57), and I possess in manuscript a 
considerable collection of additional facts, showing that simultaneous