Moreover, how little importance Linnæus himself attached to this untenable hypothesis of creation is clear, among other things, from the fact that he recognized _Hybridism_ (crossing) as a source of the production of new species. He assumed that a great number of independent new species had originated by the interbreeding of two different species. Indeed, such hybrids are not at all rare in nature, and it is now proved that a great number of species, for example, of the genus Rubus (bramble), mullen (Verbascum), willow (Salix), thistle (Cirsium), are hybrids of different species of these genera. We also know of hybrids between hares and rabbits (two species of the genus Lepus), further of hybrids between different species of dog (genus Canis), etc., which can be propagated as independent species. It is certainly very remarkable that Linnæus asserted the physiological (therefore mechanical) origin of new species in this process of hybridism. It clearly stands in direct opposition to the supernatural origin of the other species by creation, which he accepted as put forward in the Mosaic account. The one set of species would therefore have originated by dualistic (teleological) creation, the other by monistic (mechanical) development. The great and well merited authority which Linnæus gained by his systematic classification and by his other services to Biology, was clearly the reason why his views of creation also remained, throughout the whole of the last century, undisputed and generally recognized. If throughout systematic Zoology and Botany the distinctions, classification, and designations of species, introduced by Linnæus, and the dogmatic ideas connected therewith had not been maintained—more or less unaltered—we should be at a loss to understand how his idea of an independent creation of single species could have stood, by itself down to the present day. It is only owing to his great authority, and through his attaching himself to the prevailing Biblical belief, that his hypothesis of creation has retained its position so long. CHAPTER III. THE HISTORY OF CREATION ACCORDING TO CUVIER AND AGASSIZ.