306 EVOLUTION [CHAP. IV 



Letter 223 To G. H. Lewes. 1 



The following is printed from a draft letter inscribed by Mr. Darwin 

 " Against organs having been formed by direct action of medium in 

 distinct organisms. Chiefly luminous and electric organs and thorns." 

 The draft is carelessly written, and all but illegible. 



Aug. 7th, 1868. 



If you mean that in distinct animals, parts or organs, such 

 for instance as the luminous organs of insects or the electric 

 organs of fishes, are wholly the result of the external and 

 internal conditions to which the organs have been subjected, 

 in so direct and inevitable a manner that they could be 

 developed whether of use or not to their possessor, I cannot 

 admit [your view]. I could almost as soon admit that the 

 whole structure of, for instance, a woodpecker, had thus 

 originated ; and that there should be so close a relation 

 between structure and external circumstances which cannot 

 directly affect structure seems to me to [be] inadmissible. 

 Such organs as those above specified seem to me much too 

 complex and generally too well co-ordinated with the whole 

 organisation, for the admission that they result from conditions 

 independently of Natural Selection. The impression which I 

 have taken, studying nature, is strong, that in all cases, if we 

 could collect all the forms which have ever lived, we should 

 have a close gradation from some most simple beginning. 

 If similar conditions sufficed, without the aid of Natural 

 Selection, to give similar parts or organs, independently of 

 blood relationship, I doubt much whether we should have 

 that striking harmony between the affinities, embryological 

 development, geographical distribution, and geological suc- 

 cession of all allied organisms. We should be much more 

 puzzled than we now are how to class, in a natural method, 

 many forms. It is puzzling enough to distinguish between 

 resemblance due to descent and to adaptation ; but (fortunately 

 for naturalists), owing to the strong power of inheritance, and 

 to excessively complex causes and laws of variability, when 

 the same end or object has been gained, somewhat different 

 parts have generally been modified, and modified in a different 

 manner, so that the resemblances due to descent and adapta- 

 tion can commonly be distinguished. I should just like to 

 add, that we may understand each other, how I suppose the 



1 G. H. Lewes (1817-78), author of a History of ' Philosophy > etc. 



