130 
Rev. J. T. Gulick on the 
doctrine that without change in the environment there is no 
change in the organism to the fruitless truism that without 
some cause there is no change in the organism. An example 
of Mr. Wallace's extending the meaning of the environment 
so as to include the action of the members of a species on each 
other is found on page 149. After mentioning several argu- 
ments intended to show the impossibility that isolated portions 
of a species should diverge while exposed to the same environ- 
ment, he remarks, u It is impossible that the environment of 
the isolated portion can be exactly like that of the bulk of the 
species. It cannot be so physically, since no two separated 
areas can be exactly alike in climate and soil ; and, even if 
they are the same, the geographical features, size, contour, and 
relation to winds, seas, and rivers would certainly differ. 
Biologically the differences are sure to be considerable. The 
isolated portion of a species will almost always be in a much 
smaller area than that occupied by the species as a whole, hence 
it is at once in a different 'position as regards its own kind” 
He then enumerates several differences in the biological 
environment that are liable to occur ; but the point I wish 
now to note is that he mentions as one of the differences in 
the environment the u different position as regards its own 
kind” This is exactly the difference which, in so far as it is 
the prevention of intercrossing and the consequent unification 
of endowments and habits, constitutes isolation ; and unless he 
is able to show that this difference is incapable of producing 
any divergence, his contention is unsustained. But he here 
yields the point at issue by mentioning this amongst the 
effective differences. The only way to escape the force of his 
concession is to claim, as he virtually does here, that isola- 
tion, being the separation of the isolated fragment from the 
influence of the original stock, is in itself a difference in 
the environment. By taking this position, however, he 
involves himself in another contradiction, for, if isolation is a 
difference in the environment, why does he deny that it has a 
direct influence in producing change in the organism ? 
Diversity of Natural Selection during exposure to the 
same Environment . 
Another discrepancy in Mr. Wallace’s theory is that, while 
he rightly assigns great importance to diversity of natural 
selection arising from divergent habits in appropriating the 
resources of the same environment, exhibited by different 
sections of the same species occupying the same area, he 
nevertheless insists that the representatives of a species, iso- 
