the natural or necessary result of which must be to produce the present diversity of species and their actual relations; or, 2.  To show the general conformity of the whole body of facts to such assumption, and also to adduce instances explicable by it and inexplicable by the received view, so perhaps winning our assent to the doctrine, through its competency to harmonize all the facts, even though the cause of the assumed variation remain as occult as that of the transformation of tadpoles into frogs, or that of Coryne into Sarzia.

The first line of proof, successfully carried out, would establish derivation as a true physical theory; the second, as a sufficient hypothesis.

Lamarck mainly undertook the first line, in a theory which has been so assailed by ridicule that it rarely receives the credit for ability to which in its day it was entitled, But he assigned partly unreal, partly insufficient causes; and the attempt to account for a progressive change in species through the direct influence of physical agencies, and through the appetencies and habits of animals reacting upon their structure, thus causing the production and the successive modification of organs, is a conceded and total failure.  The shadowy author of the “Vestiges of the Natural History of Creation” can hardly be said to have undertaken either line, in a scientific way.  He would explain the whole progressive evolution of Nature by virtue of an inherent tendency to development, thus giving us an idea or a word in place of a natural cause, a restatement of the proposition instead of an explanation.  Mr. Darwin attempts both lines of proof, and in a strictly scientific spirit; but the stress falls mainly upon the first, for, as he does assign real causes, he is bound to prove their adequacy.

It should be kept in mind that, while all direct proof of independent origination is attainable from the nature of the case, the overthrow of particular schemes of derivation has not established the opposite proposition.  The futility of each hypothesis thus far proposed to account for derivation may be made apparent, or unanswerable objections may be urged against it; and each victory of the kind may render derivation more improbable, and therefore specific creation more probable, without settling the question either way.  New facts, or new arguments and a new mode of viewing the question, may some day change the whole aspect of the case.  It is with the latter that Mr. Darwin now reopens the discussion.

Having conceived the idea that varieties are incipient species, he is led to study variation in the field where it shows itself most strikingly, and affords the greatest facilities to investigation.  Thoughtful naturalists have had increasing grounds to suspect that a reexamination of the question of species in zoology and botany, commencing with those races which man knows most about, viz., the domesticated and cultivated races, would be likely somewhat to