1870-1SS2] bentham's address 379 



To G. Bentham. Letter 290 



Down, Nov. 25th, 1869. 

 The notes to this letter are by Sir W. Thiselton-Dyer, and appeared 

 in Nature, loc, cit. 



I was greatly interested by your address, which I have 

 now read thrice, and which I believe will have much influence 

 on all who read it. But you are mistaken in thinking that I 

 ever said you were wrong on any point. All that I meant 

 was that on certain points, and these very doubtful points, I 

 was inclined to differ from you. And now, on further con- 

 sidering the point on which some two or three months ago I 

 felt most inclined to differ — viz., on isolation — I find I differ 

 very little. What I have to say is really not worth saying, 

 but as I should be very sorry not to do whatever you asked, 

 1 will scribble down the slightly dissentient thoughts which 

 have occurred to me. It would be an endless job to specify 

 the points in which you have interested me ; but I may just 

 mention the relation of the extreme western flora of Europe 

 (some such very vague thoughts have crossed my mind, 

 relating to the Glacial period) with South Africa, and your 

 remarks on the contrast of passive and active distribution. 



P. lxx. — I think the contingency of a rising island, not as 

 yet fully stocked with plants, ought always to be kept in 

 mind when speaking of colonisation. 



P. lxxiv.— I have met with nothing which makes me in 

 the least doubt that large genera present a greater number 

 of varieties relatively to their size than do small genera. 1 

 Hooker was convinced by my data, never as yet published 

 in full, only abstracted in the Origin. 



P. lxxviii. — I dispute whether a new race or species is 

 necessarily, or even generally, descended from a single or pair 

 of parents. The whole body of individuals, I believe, become 

 altered together — like our race-horses, and like all domestic 



1 Bentham thought " degree of variability . . . like other constitu- 

 tional characters, in the first place an individual one, which . . . may 

 become more or less hereditary, and therefore specific ; and thence, but 

 in a very faint degree, generic." He seems to mean to argue against 

 the conclusion which Sir Joseph Hooker had ([noted from Mr. Darwin 

 that "species of large genera are more variable than those of small." 

 [On large genera varying, see Letter 53.] 



