A critical examination of some of the principal arguments for and against Darwinism / by James Maclaren.
- MacLaren, James
- Date:
- 1876
Licence: Public Domain Mark
Credit: A critical examination of some of the principal arguments for and against Darwinism / by James Maclaren. Source: Wellcome Collection.
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![turbed. Nothing can be effected unless favourable variations occur, and variation itself is apparently always a very slow pro- cess ; the process will often be greatly retarded by free intercrossing. Many, says Mr Darwin, will exclaim that these several causes are am]3ly sufficient wholly to stop the action of natural selection ; he does not think so. On the other hand, he says, he does believe that natural action will always act very slowly, often only at long- intervals of time, and generally on only a very few of the inhabit- ants of the same region at the same time. Mr Darwin makes these admissions because the variations are so small and so rare that they escape our perceptions until tliey are accumulated. Tlie long interval supposed to exist between the variations may seem opposed to Mr Darwin’s notion of natural selection being always at work, but we must remember that in jDroportion as the period of time during which tliey occur and are ac- cumulated is long, so the variations called infrequent may be both numerous and, in comparison, rapid. But on this supposition how vast is the period of time necessary to](https://iiif.wellcomecollection.org/image/b28077416_0060.jp2/full/800%2C/0/default.jpg)
