Alfred Russel Wallace : Alfred Wallace : A. R. Wallace :
Russel Wallace : Alfred Russell Wallace (sic)
Discussion of Rev. John T. Gulick's 'On the
Difficulties of Darwinism' (S212: 1872)
Editor Charles H. Smith's Note: A third person summary of Wallace's comments on a paper by the
Rev. John T. Gulick delivered at the 1872 annual meetings of the British Association for the
Advancement of Science, as recorded on page 407 of the 12 September 1872 issue of Nature. To
link directly to this page connect with: http://people.wku.edu/charles.smith/wallace/S212.htm
Mr. Wallace agreed with the Rev. J. T. Gulick in his interpretation of facts which appeared to
be exceedingly remarkable. He had had the opportunity of working at a limited group of organisms
in a small part of the world. The results he had described were a type of what took place over
whole continents, and exhibit an example of variation and geographical distributions, perhaps the
most remarkable that occurs on the surface of the earth. With the general principle that variation
does not depend on difference in external condition, he altogether agreed. He thought in this matter
that there was a confusion of two distinct things, even in some cases by Mr. Darwin himself.
Variation was confounded with the formation of varieties. That it was not dependent on the change
of conditions was evidenced by the fact that the varieties of domestic animals and plants were not
due to this cause, but only to advantage being taken of spontaneous variation and identical
conditions. Horticulturists obtained new varieties of any plant that was introduced into cultivation
by growing it upon a very large scale, and selecting the sports which were sure to occur. In this
case variation was accumulated by artificial selection, just as it is accumulated in nature by natural
selection. This requires, as a condition of its action, a change of external conditions. We all know
that closely allied, though distinct species, were found inhabiting distinct areas--for example,
islands; and with large continental areas it was the same. This had led to the very general idea that
it was variation of condition over those areas which had produced the varieties, whereas it had
merely selected them. In the Sandwich Islands there was no difference of physical conditions
adequate to produce this result. This was seen in the number of intervening forms which existed. It
seemed due to the absence of any weeding-out effect. The land molluscs had hardly any
competitors to struggle with, and no enemies, quadrupeds and reptiles being absent, and birds few.
The rivers were small and would only distribute any form through the same valley. All these
conditions favoured this remarkable persistence of closely linked forms.
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