Thus several, and perhaps the majority, of our younger naturalists have been seduced into the acceptance of the homoeopathic form of the transmutative hypothesis now presented to them by Mr. Darwin, under the phrase of 'natural selection.'
Mr. Wallace calls attention to the 'tremendous rate of increase in a few years from a single pair of birds producing two young ones each year, and this only four times in their life; in fifteen years such pair would have increased to nearly ten millions!' (22) The passenger-pigeon of the United States exemplifies such rate of increase, where congenial food abounds. But, as a general rule, the animal population of a country is stationary, being kept down by a periodical deficiency of food and other checks. Hence the struggle for existence; and the successful result of adapted organisation and powers in a well developed variety, which Mr. Darwin generalises as 'Natural Selection,' and which Mr. Wallace (23) illustrates as follows: —
Bear whale Edit
But of this, in the absence of a definition of the starting point, we cannot be perfectly sure. 'Natural selection' may operate in both directions. The following, for example, would have been cordially welcomed by Buffon as a testimony in favour of his 'dégénération' hypothesis: —
'In North America the black bear was seen by Hearne swimming for hours with widely open mouth, thus catching, like a whale, insects in the water. Even in so extreme a case as this, if the supply of insects were constant, and if better adapted competitors did not already exist in the country, I can see no difficulty in a race of bears being rendered, by natural selection, more and more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale.' (40)
(41) But the close resemblance of the style, and of the tone and frame of mind which could see no difficulty in the adequacy of the above-cited circumstances of 'external conditions, of habit, of volition,' to change a bear into a whale, to those exemplified in the Philosophie Zoologique, point strongly to the writings of Lamarck as the true suggestor of Mr. Darwin's views of animated nature.
Demaillet, it must be admitted, enters more fully into the details of the operation of 'natural selection,' in changing the fish into the bird; and it is, perhaps, from this very 'naïveté' in the exposition of his theory, that its weakness has been made so obvious to later zoologists and comparative anatomists. Mr. Darwin rarely shows a fair front to these searching tests; the facts of the manner of transmutation, as they might have presented themselves to his fancy, are not stated with the 'abandon' of the old French philosopher. Vague and general as is the illustration based upon Hearne's remark, it is made still more vague in a later reprint of the volume On the Origin of Species.
It now reads, 'In North America the black bear was seen by Hearne swimming for hours with widely opened mouth, thus catching, almost like a whale, insects in the water.' (Ed. 1860, p. 184.)
Owen identifies tautology Edit
Darwin wrote: 'Although I do not doubt that isolation is of considerable importance in the production of new species, on the whole, I am inclined to believe, that largeness of area is of more importance in the production of species capable of spreading widely.' (P. 105.)
Owen replies: We readily concede ... the fact ... that the wider the area in which a species may be produced, the more widely it will spread. But we fail to discern its import in respect of the great question at issue.