SKETCH OF 1844. 13, 



under " Difficulties on Theory." The second part seems to 

 have been planned in accordance with his favourite point of 

 view with regard to his theory. This is briefly given in a 

 letter to Dr. Asa Gray, November nth, 1859: "I cannot 

 possibly believe that a false theory would explain so many 

 classes of facts, as I think it certainly does explain. On these 

 grounds I drop my anchor, and believe that the difficulties 

 will slowly disappear." On this principle, having stated the 

 theory in the first part, he proceeds to show to what extent 

 various wide series of facts can be explained by its means. 



Thus the second part of the Sketch corresponds roughly 

 to the nine concluding Chapters of the First Edition of the 

 'Origin.' But we must exclude Chapter VII. ('Origin') on 

 Instinct, which forms a chapter in the first part of the Sketch, 

 and Chapter VIII. ('Origin') on Hybridism, a subject treated 

 in the Sketch with 'Variation under Nature ' in the first part. 



The following list of the chapters of the second part of the 

 Sketch will illustrate their correspondence with the final 

 chapters of the ' Origin.' 



Chapter I. " On the kind of intermediateness necessary, 

 and the number of such intermediate forms." 



This includes a geological discussion, and corresponds to 

 parts of Chapters VI. and IX. of the ' Origin.' 



Chapter II. "The gradual appearance and disappearance 

 of organic beings." Corresponds to Chapter X. of the 

 ' Origin.' 



Chapter III. " Geographical Distribution." Corresponds to 

 Chapters XI. and XII. of the 'Origin.' 



Chapter IV. " Affinities and Classification of Organic 

 beings." 



Chapter V. " Unity of Type," Morphology, Embryology. 



Chapter VI. Rudimentary Organs. 



These three chapters correspond to Chapter XII. of the 

 ' Origin.' 



Chapter VII. Recapitulation and Conclusion. The final 



