438 THE UNFINISHED BOOK. [1856 



me) have to be explained by climatal and geological changes. 

 A fortiori on this view (but on exactly same grounds), all the 

 individuals of the same species should have a continous dis- 

 tribution. On this latter branch of the subject I have put a 

 chapter together, and Hooker kindly read it over. I thought 

 the exceptions and difficulties were so great that on the whole 

 the balance weighed against my notions, but I was much 

 pleased to find that it seemed to have considerable weight 

 with Hooker, who said he had never been so much staggered 

 about the permanence of species. 



I must say one word more in justification (for I feel sure 

 that your tendency will be to despise me and my crotchets), 

 that all my notions about how species change are derived 

 from long continued study of the works of (and converse 

 with) agriculturists and horticulturists ; and I believe I see 

 my way pretty clearly on the means used by nature to change 

 her species and adapt them to the wondrous and exquis- 

 itely beautiful contingencies to which every living being is 

 exposed. . . . 



C. Darwin to J. D. Hooker. 



Down, July soth, 1856. 



MY DEAR HOOKER, Your letter is of much value to me. 

 I was not able to get a definite answer from Lyell,* as you 

 will see in the enclosed letters, though I inferred that he 

 thought nothing of my arguments. Had it not been for this 

 correspondence, I should have written sadly too strongly. 

 You may rely on it I shall put my doubts moderately. There 

 never was such a predicament as mine : here you continental 

 extensionists would remove enormous difficulties opposed to 

 me, and yet I cannot honestly admit the doctrine, and must 

 therefore say so. I cannot get over the fact that not a frag- 

 ment of secondary or palaeozoic rock has been found on any 

 island above 500 or 600 miles from a mainland. You rather 

 misunderstand me when you think I doubt the possibility ot 



* On the continental extensions of Forbes and others. 



