Analogous facts to those occur in other classes of animals, as an example of which we have the authority of a distinguished paleontologist, M. Barande, quoted by Mr. Darwin, for the statement, that although the Palæozoic Invertebrata can certainly be classed under existing groups, yet at this ancient period the groups were not so distinctly separated from each other as they are now; while Mr. Scudder tells us, that some of the fossil insects discovered in the Coal formation of America offer characters intermediate between those of existing orders. Agassiz, again, insists strongly that the more ancient animals resemble the embryonic forms of existing species; but as the embryos of distinct groups are known to resemble each other more than the adult animals (and in fact to be undistinguishable at a very early age), this is the same as saying that the ancient animals are exactly what, on Darwin’s theory, the ancestors of existing animals ought to be; and this, it must be remembered, is the evidence of one of the strongest opponents of the theory of natural selection.
Conclusion.
I have thus endeavoured to meet fairly, and to answer plainly, a few of the most common objections to the theory of natural selection, and I have done so in every case by referring to admitted facts and to logical deductions from those facts.
As an indication and general summary of the line of argument I have adopted, I here give a brief demonstration in a tabular form of the Origin of Species by means of Natural Selection, referring for the facts to Mr. Darwin’s works, and to the pages in this volume, where they are more or less fully treated.
A Demonstration of the Origin of Species by Natural Selection.
| PROVED FACTS | NECESSARY CONSEQUENCES (afterwards taken as Proved Facts). |
| Rapid Increase of Organisms, pp. 29, 265; (“Origin of Species,” p. 75, 5th Ed.) | Struggle for Existence, the deaths equalling the births on the average, p. 30; (“Origin of Species,” chap. III.) |
| Total Number of Individuals Stationary, pp. 30, 266. | |
| Struggle for Existence. | Survival of the Fittest, or Natural Selection; meaning simply, that on the whole those die who are least fitted to maintain their existence; (“Origin of Species,” chap. IV.) |
| Heredity With Variation, or general likeness with individual differences of parents and offspring, pp. 266, 287-291, 308; (“Origin of Species,” chap. I., II., V.) | |
| Survival of the Fittest. | Changes of Organic Forms, to keep them in harmony with the Changed Conditions; and as the changes of conditions are permanent changes, in the sense of not reverting back to identical previous conditions, the changes of organic forms must be in the same sense permanent, and thus originate Species. |
| Change of External Conditions, universal and unceasing.—See “Lyell’s Principles of Geology.” |