162 EVOLUTION [CHAP. Ill 



Letter no You object to all my illustrations. They are all neces- 

 sarily conjectural, and may be all false ; but they were the 

 best I could give. The bear case 1 has been well laughed at, 

 and disingenuously distorted by some into my saying that 

 a bear could be converted into a whale. As it offended 

 persons, I struck it out in the second edition ; but I still 

 maintain that there is no especial difficulty in a bear's mouth 

 being enlarged to any degree useful to its changing habits, 

 no more difficulty than man has found in increasing the crop 

 of the pigeon, by continued selection, until it is literally as 

 big as the whole rest of the body. If this had not been 

 known, how absurd it would have appeared to say that the 

 crop of a bird might be increased till it became like a 

 balloon ! 



With respect to the ostrich, I believe that the wings have 

 been reduced, and are not in course of development, because 

 the whole structure of a bird is essentially formed for flight ; 

 and the ostrich is essentially a bird. You will see at p. 182 

 of the Origin a somewhat analogous discussion. At p. 450 

 of the second edition I have pointed out the essential dis- 

 tinction between a nascent and rudimentary organ. If you 

 prefer the more complex view that the progenitor of the 

 ostrich lost its wings, and that the present ostrich is regaining 

 them, I have nothing to say in opposition. 



With respect to trees on islands, I collected some cases, 

 but took the main facts from Alph. De Candolle, and thought 

 they might be trusted. My explanation may be grossly 

 wrong ; but I am not convinced it is so, and I do not see 

 the full force of your argument of certain herbaceous orders 

 having been developed into trees in certain rare cases on 

 continents. The case seems to me to turn altogether on the 

 question whether generally herbaceous orders more frequently 

 afford trees and bushes on islands than on continents, 

 relatively to their areas. 2 



1 Origin of Species, Ed. I., p. 184. See Letter 120. 



2 In the Origin, Ed. I., p. 392, the author points out that in the 

 presence of competing trees an herbaceous plant would have little chance 

 of becoming arborescent ; but on an island, with only other herbaceous 

 plants as competitors, it might gain an advantage by overtopping its 

 fellows, and become tree-like. Harvey writes : " What you say (p. 392) 

 of insular trees belonging to orders which elsewhere include only 



