Volume 1

The variation of animals and plants under domestication / by Charles Darwin.

  • Charles Darwin
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: The variation of animals and plants under domestication / by Charles Darwin. Source: Wellcome Collection.

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    exists to the number, singularity, and perfection of the contrivances and co-adaptations which may thus be pro- duced. An animal or a plant may thus slowly become related in its structure and habits in the most intricate manner to many other animals and plants, and to the physical conditions of its home. Variations in the organiza- tion will in some cases be aided by habit, or by the use and disuse of parts, and they will be governed by the direct action of the surrounding physical conditions and by correlation of growth. On the principles here briefly sketched out, there is no innate or necessary tendency in each being to its own ad- vancement in the scale of organization. We are almost compelled to look at the specialization or differentiation of parts or organs for different functions as the best or even sole standard of advancement; for by such division of labour each function of body and mind is better performed. And as natural selection acts exclusively through the preservation of profitable modications of structure, and as the conditions of life in each area generally become more and more complex from the increasing number of different forms which inhabit it and from most of these forms acquiring a more and more perfect structure, we may confidently believe, that, on the whole, organization advances. Nevertheless a very simple form fitted for very simple conditions of life might remain for indefinite ages unaltered or unimproved ; for what would it profit an infusorial animalcule, for instance,-or an intestinal worm, to become highly organized ? Members of a high group might even become, and this apparently has often occurred, fitted for simpler conditions of life ; and in this case natural selection would tend to simplify or degrade the organization, for complicated mechanism for simple actions would be useless or even disadvantageous. The arguments opposed to the theory of Natural Selection, have been discussed in my ‘ Origin of Species,’ as far as the size of that work permitted, under the following heads : the difficulty in understanding how very simple organs have been converted by small and graduated steps into highly perfect and complex organs; the marvellous facts of
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