The Making of Species 
“Tt does not seem possible to maintain the 
contention that these various species are the 
products of natural selection, for that would 
mean if the black of the head of the Punjab 
species extended further into the neck the bird 
could not live in that country.” 
Thus, natural selection clearly is unable to 
explain some cases of divergence of character 
due to geographical isolation. 
There remains the third explanation, that the 
divergence is the result of the simple fact of 
isolation. 
We have already shown how insuperable are 
the objections to the view held by Romanes and 
Gulick. 
It seems to us that explanation must lie in the 
fact that mutations occur every now and again in 
some species. If two portions of a species are 
separated and a mutation occurs in one portion 
and not in the other, and if the mutating form 
succeeds in supplanting the parent form in that 
isolated portion of the species in which it has 
appeared, we should have the phenomenon of 
two races or species differing in appearance 
although subjected to what appear to be identical 
environment. 
This, of course, is pure conjecture. All that 
can be said of it at present is that it is not 
opposed to observed facts. That mutations do 
occur must be admitted. At present we are 
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