2 INTBOD UCTION. 



and Dr. Hooker, who both knew of my work— the latter 

 having read my sketch of 1844— honored me by thinking 

 it advisable to publish, with Mr. Wallace's excellent memoir, . 

 some brief extracts from my manuscripts. 



This abstract, which I now publish, must necessarily 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 

 may have crept in, though I hope I have always been cau- 

 tious in trusting to good authorities alone. I can here give 

 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 more sensible than I do of 

 the necessity of hereafter publishing in detail all the facts, 

 with references, on which my 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 ap- 

 parently leading to conclusions directly opposite to those 

 at which I have arrived. A fair result can be obtained 

 only by fully stating and balancing the facts and arguments 

 on both sides of each question; and this is here impossible. 



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 conceiv- 

 able that a naturalist, reflecting on the mutual affinities of 

 organic beings, on their embryological relations, their 

 geographical distribution, geological succession, and other 

 such facts, might come to the conclusion that species had 

 not_ been independently created, but had descended, like 

 varieties, from other species. Nevertheless, such a con- 

 clusion, even if well founded, would be unsatisfactory, until 

 it could be shown how the innumerable species, inhabit- 

 ing this world have been modified, so as to acquire that 

 perfection of structure and coadaptation which justly 

 excites pur admiration. Naturalists continually refer to 



