18441858] NATURAL SELECTION 41 



(quite contrary to the opinion I started with) that species Letter 13 

 are not (it is like confessing a murder) immutable. Heaven 

 forfend me from Lamarck nonsense of a " tendency to pro- 

 gression," " adaptations from the slow willing of animals," 

 etc. ! But the conclusions I am led to are not widely different 

 from his ; though the means of change are wholly so. I think 

 I have found out (here's presumption !) the simple way by 

 which species become exquisitely adapted to various ends. 

 You will now groan, and think to yourself, "on what a man 

 have I been wasting my time and writing to." I should, five 

 years ago, have thought so. ... 1 



To J. D. Hooker. Letter 14 



[Nov.] 1844. 



. . . What a curious, wonderful case is that of the 

 Ly cop odium ! 2 . . . I suppose you would hardly have expected 

 them to be more varying than a phanerogamic plant. I trust 

 you will work the case out, and, even if unsupported, publish 

 it, for you can surely do this with due caution. I have heard 

 of some analogous facts, though on the smallest scale, in 

 certain insects being more variable in one district than in 

 another, and I think the same holds with some land-shells. 

 By a strange chance I had noted to ask you in this letter an 

 analogous question, with respect to genera, in lieu of individual 

 species, that is, whether you know of any case of a genus 

 with most of its species being variable (say Rubus) in one 

 continent, having another set of species in another continent 

 non-variable, or not in so marked a manner. Mr. Herbert 3 

 incidentally mentioned in a letter to me that the heaths at 

 the Cape of Good Hope were very variable, whilst in Europe 

 they are (?) not so ; but then the species here are few in 

 comparison, so that the case, even if true, is not a good one. 

 In some genera of insects the variability appears to be common 



1 On the questions here dealt with see the interesting letter to 

 Jenyns in the Life and Letters, II., p. 34. 



2 Sir J. D. Hooker wrote, Nov. 8, 1844 : " I am firmly convinced 

 (but not enough to print it) that L. Selago varies in Van Diemen's Land 

 into L. variant. Two more different species (as they have hitherto been 

 thought), per se cannot be conceived, but nowhere else do they vary into 

 one another, nor does Selago vary at all in England." 



3 No doubt Dean Herbert, the horticulturist. See Life and Letters, 



I-, P- 343- 



