Contributions To The Theory Of Natural Selection; A Series Of Essays

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: 28 ON THE TENDENCY OF VAEIETIES TO DEPART INDEFINITELY FROM THE ORI... Read more

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: 28 ON THE TENDENCY OF VAEIETIES TO DEPART INDEFINITELY FROM THE ORIGINAL TYPE. Instability of Varieties supposed to prove the permanent distinctness of Species. Okb of the strongest arguments which have been adduced to prove the original and permanent distinctness of species is, that varieties produced in a state of domesticity are more or less unstable, and often have a tendency, if left to themselves, to return to the normal form of the parent species; and this instability is considered to be a distinctive peculiarity of all varieties, even of those occurring among wild animals in a state of nature, and to constitute a provision for preserving unchanged the originally created distinct species. In the absence or scarcity of facts and observations as to varieties occurring among wild animals, this argument has had great weight with naturalists, and has led to a very general and somewhat Written at Ternate, February, 1858; and published in the Journal of the Proceedings of the Linnsean Society for August, 1858. prejudiced belief in the stability of species. Equally general, however, is the belief in what are called permanent or true varieties, ?races of animals which continually propagate their like, but which differ so slightly (although constantly) from some other race, that the one is considered to be a variety of the other. Which is the variety and which the original species, there is generally no means of determining, except in those rare cases in which the one race has been known to produce an offspring unlike itself and resembling the other. This, however, would seem quite incompatible with the permanent invariability of species, but the difficulty is overcome by assuming that such varieties have strict limits, and can never again vary further from th... Less