14. That vegetables and animals, being once placed upon the earth, have multiplied or are multiplying, so as to occupy every part of the land and water which is suited for their habitation, we can see much reason to believe. Philosophical natural-historians have been generally led to the conviction that each species has had an original centre of dispersion, where it was first native, and that from this centre it has been diffused in all directions, as far as the circumstances of climate and soil were favorable to its production. But we can see also much reason to believe that this general diffusion of vegetable and animal life from centres, is a part of the order of nature which may often be made to give way to other and higher purposes;--to the diffusion, over the whole surface of the earth, of a race of intelligent, moral agents. This process may often interfere with the general law of diffusion: as for instance, when man exterminates noxious animals. And whatever may be the laws which tend to replenish the earth, on which such centres of the diffusion of life exist for animals and plants; according to all analogy, these laws can have no force on any other planet, till such origins and centres of life are established on their surfaces. And even if any of the species which have ever tenanted the earth were so established on any other planet, we have the strongest reason to believe that they could not survive to a second generation. 15. Perhaps it may be said that we unjustifiably limit the power and skill of the Supreme Creator, if we deny that he could frame creatures fitted to live on any of the other planets, as well as in the Earth:--that the wonderful variety, and unexpected resource, of the ways in which animals are adapted for all kinds of climates, habitations, and conditions, upon the earth, may give us confidence that, under conditions still more extended, in habitations still further removed, in climates going beyond the terrestrial extremes, still the same wisdom and skill may well be supposed to have devised possible modes of animal life.