l8o SPREAD OF EVOLUTION. [1862. 



C. Darwin to C. Lyell. 



I Carlton Terrace, Southampton,* 

 Aug. 22, [1862]. 



.... I heartily hope that you \ will be out in October. 

 . . . . You say that the Bishop and Owen will be down on 

 you ; the latter hardly can, for I was assured that Owen 

 in his Lectures this spring advanced as a new idea that 

 wingless birds had lost their wings by disuse, also that 

 magpies stole spoons, &c., from a 7'emnant of some instinct 

 like that of the Bower-Bird, which ornaments its playing- 

 passage with pretty feathers. Indeed, I am told that he 

 hinted plainly that all birds are descended from one .... 



Your P.S, touches on, as it seems to me, very difficult 

 points. I am glad to see [that] in the * Origin,' I only say 

 that the naturalists generally consider that low organisms 

 vary more than high ; and this I think certainly is the 

 general opinion. I put the statement this way to show that 

 I considered it only an opinion probably true. I must own 

 that I do not at all trust even Hooker's contrary opinion, as 

 I feel pretty sure that he has not tabulated any result. I 

 have some materials at home, I think I attempted to make 

 this point out, but cannot remember the result. 



Mere variability, though the necessary foundation of all 

 modifications, I believe to be almost always present, enough 

 to allow of any amount of selected change ; so that it does 

 not seem to me at all incompatible that a group which at any 

 one period (or during all successive periods) varies less, 

 should in the long course of time have undergone more mod- 

 ification than a group which is generally more variable. 



Placental animals, e. g. might be at each period less vari- 

 able than Marsupials, and nevertheless have undergone more 

 diffei^entiation and development than marsupials, owing to 

 some advantage, probably brain development. 



* The house of his son William. 

 \ I.e.' The Antiquity of Man.' 



