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being rendered by natural selection more and more aquatic in their 
structure and habits, with large and larger mouths, till a creature 
was produced as monstrous as a whale” (p. 184).* And the final 
conclusion to which he has arrived is summed up as follows : — * 
■ ‘ Analogy would lead me one step farther, namely, to the belief 
that all animals and plants have descended from some one prototype. 
But analogy may be a deceitful guide. Nevertheless, all living things 
have much in common in their chemical composition, their germinal 
vesicles, their cellular structure, and their laws of growth and re- 
production. Therefore, I should infer from analogy, that probably 
all the organic beings which have ever lived on this earth have de- 
scended from some one primordial form into which life was first 
breathed” (p. 484). 
Such is a general statement of the position taken by Mr Darwin ; 
and in support of it, as might be anticipated from so accomplished 
a naturalist, we have in his work not only the chief arguments on 
which it rests ably stated, but numerous phenomena and facts in 
natural history applied to it. so as to test its probability by its 
consistency or inconsistency with them. These illustrations form, 
however, only a very small portion of the facts which he has accumu- 
lated, and which, he informs us, will be afterwards published in 
a larger and more elaborate treatise, and are now to be looked 
upon as no more than mere indications of the nature of the evi- 
dence he possesses, and proposes hereafter to adduce. A few of the 
most important of these I shall briefly notice, but I think their 
value may be perhaps better appreciated if I first state what I con- 
sider to be the essential qualities requisite for the existence and 
preservation of a species. I conceive that all species bear implanted 
within them two essential laws, without which they could not exist. 
The one, a power of accommodating themselves to a certain extent 
to circumstances ; in other words, a power of modification or varia- 
tion, as Darwin calls it. Without this the individuals composing the 
* In quoting this, I do not at all mean to give it as a fair illustration of Mr 
Darwin’s views. I only refer to it as indicating the extent to which he is 
prepared to go. The example here given I look upon (as I have reason to 
know Mr Darwin does himself ) merely as an extreme and somewhat extrava- 
gant illustration, imagined expressly to show in a forcible way how “ natural 
selection ” would operate in making a mouth bigger and bigger, because more 
advantageous. 
