488 GEOGRAPHICAL DISTRIBUTION [CHAP. VI 



Letter 370 modified in Madeira. 1 Pray look at p. 422 of Origin [Ed. III.]. 

 You would not think it a mystery if you had seen the long 

 lists which I have (somewhere) of the birds annually blown, 

 even in flocks, to Madeira. The crossed stock would be the 

 more vigorous. 



Remember if you do not come here before Nottingham, 

 if you do not come afterwards I shall think myself diabolically 

 ill-used. 



Letter 371 J- D. Hooker to C. Darwin. 



Kew, Aug. Qth, 1866. 



If my letters did not gene you it is impossible that you 

 should suppose that yours were of no use to me ! I would 

 throw up the whole thing were it not for correspondence with 

 you, which is the only bit of silver in the affair. I do feel it 

 disgusting to have to make a point of a speciality in which I 

 cannot see my way a bit further than I could before I began. 

 To be sure, I have a very much clearer notion of the pros and 

 cons on both sides (though these were rather forgotten facts 

 than rediscoveries). I see the sides of the well further down 

 more distinctly, but the bottom is as obscure as ever. 



I think I know the Origin by heart in relation to the 

 subject, and it was reading it that suggested the queries about 

 Azores boulders and Madeira birds. The former you and 

 I have talked over, and I thought I remembered that you 

 wanted it confirmed. The latter strikes me thus : why should 

 plants and insects have been so extensively changed and birds 

 not at all ? I perfectly understand and feel the force of your 

 argument in reference to birds per se, but why do these not 

 apply to insects and plants ? Can you not see that this 

 suggests the conclusion that the plants are derived one way 

 and the birds another? 



I certainly did take it for granted that you supposed the 



1 Origin, Ed. VI., p. 328. Madeira has only one endemic bird. 

 Darwin accounts for the fact from the island having been stocked with 

 birds which had struggled together and become mutually co-adapted on 

 the neighbouring continents. " Hence, when settled in their new homes, 

 each kind will have been kept by the others in its proper place and 

 habits, and will consequently have been but little liable to modification." 

 Crossing with frequently arriving immigrants will also tend to keep down 

 modification. 



