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THE GEOLOGIST. 
SOME REMARKS ON MR. DARWIN'S THEORY. 
By Frederick Wollastoh Hutton, F.G.S. 
I said that " all the years invent ; 
Each month is various to present 
The world with some development." — Tennyson. 
Although most of my readers will be perfectly acquainted with the 
theory proposed by Mr. Darwin to account for the various forms of 
life that we see on the globe, yet, for the sake of clearness, I will 
briefly enunciate it. 
Mr. Darwin first shows that individuals of the same species vary 
one with another. 
He then shows that, owing to the rapid increase of animal and vege- 
table life, by which many more are born each year than can possibly 
survive, there is a continual warfare going on among them for food 
and other necessaries. This he calls the " struggle for life." 
He then shows that if any animal or plant should have, by varia- 
tion, any organ or property so modified as to give it some advantage 
over its fellows in the struggle for life, it will, as a general rule, live 
longer and produce more offspriag ; and these offspring will have a 
tendency to inherit the organ or property modified in the same man- 
ner : but if in one of these offspring the organ should be still further 
modified, it will give him a like advantage over his brethren, and his 
offspring agaia will have a tendency to reproduce the organ in its 
more modified state ; and so on. This he calls Natural Selection." 
Mr. Darwin thinks that this, together ^vith the minor causes of 
habit, use and disuse, climate, &c., are sufficient to account for all the 
various forms of organic life, by the gradual transmutation of one 
species into another. 
As all naturalists allow that species vary, it seems that the difference 
in the opinions of some of them on this subject arise on the question 
of limits. Are these varieties of species limited, or are they unlimited ? 
A limiting value of a variable is a quantity to which the variable 
may approach ever so near, but never reach ; if therefore it can be 
shown that there is a limiting value to the variation of species, Mr. 
Darwin's theory could not be extended beyond that limit. At present 
no one has been able to assign to it any limits at all ; in fact it will be a 
very difficult thing to do so, for it would be of no use to prove that 
any one organ of a paiiicular animal could not change into the rare 
organ of another particular animal, as it is never supposed that the 
higher form of life has passed through every lower form ; for the same 
reason that the sap which nourishes one leaf of a tree has not passed 
through all the other leaves. 
The way this question has generally been argued is, not by trying 
to define any one strict limit beyond which variation cannot pass, but 
