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Show 10 INTRODUCTION Charles Lyell, who sent it to the Linnean Society, and it is published in the third volume of the Journal of that Society. Sir C. Lyell and Dr. Hooker, who both knew of my work-the latter having read my sketch of 1844 -honoured me by thinking it ~dvisable ~o publish, with Mr. Wallace's excellent memoir, some bnef extracts froin my manuscripts.. . . This Abstract, which I now pubhsh, must necessanly be imperfect. I cannot here give references and authorities for my several statements ; and I must trust to the reader reposing some confidence in my accuracy. No doubt errors will have crept in, though I hope I have always been. cautious in trusting to good a?-thorif s ~lone. I can here g1ve only the general conclusions ·at whiCh I have arrived, with a few facts in illustration, but which, I hope, in most cases will suffice. No one can feel 1nore sensible than I do of the necessity of hereafter publishing in detail all the facts, with references, on which Iny conclusions have been grounded; and I hope in a future work to do this. For I am well aware that scarcely a single point is discussed in this volume on which facts cannot be adduced, often apparently leading to conclusions directly opposite to those at which I hav~ arrived. A ~air result can be obtained only by fully stating and balanmng the facts and arguments on both sides of each question ; and this cannot possibly be here done. I much regret that want of space prevents my having the satisfaction of acknowledging the generous assistance which I have received from very many naturalists, some of them personally unknown to me. I cannot, however, let this opportunity pass without expressing my deep obligations to Dr. Hooker, who for the last fifteen years has aided me in every possible way by his large stores of knowledge and his excellent judgment. In considering the Origin of Species, it is quite conceivable that a naturalist, reflecting on the mutual affini- . ties of organic beings, on their mnbryological relations, their geographical d~stribution, geological succession, and other such facts, might come to the conclusion that each species had not been independently created, but had de· INTRODUCTION. 11 scended, like varieties, from other species. Nevertheless such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified so as to acq_uire that. perfectioJ?- of structu~e ~nd coadaptation whiCh most JUStly excites our adinJrahon. Naturalists continually refer to external conditions, such as climate, food, &c., as the only possible cause of variation. In one very limited sense, as we shall hereafter see, this may be true ; but it is preposterous to attribute to mere external conditions, the structure, for instance, of the woodpecker, with its feet, tail, beak, and tongue, so admirably adapted to catch insects under the bark of trees. In the case of the n1isseltoe, which draws its· nourishment from certain trees, which has seeds that must be transported by certain birds, and which has flowers with separate sexes absolutely requiring the agency of certain insects to bring pollen from one flower to the other, it is equally preposterous to account for the structure of this parasite, with its relations to several distinct organic beings, by the effects of external conditions, or of habit, or of the volition of the plant itself. The author of the 'Vestiges of Creation ' would, I presume, say that, after a certain number of generations, some bird had given birth to a woodpecker, and some plant to the misseltoe, and that these had peen produced perfect as we now see them ; but this assumption seems to me to be no explanation, for it leaves the case of the coadaptations of organic beings to each other and to their physical conditions of life, untouched and unexplained. It is, therefore, of the hi~hest importance to gain a clear insight into the means of modification and coadaptation. At the commencement of my observations it seemed to me probable that a careful study of domesticated animals and of cultivated plants would offer the best chance of making out this obscure problem. Nor have I been disappointed ; in this and in all other perplexing cases I have invariably found that our knowledge, imperfect though it be, of variation under domestication, afforded the best and safest clue. I may venture to express. my |