.1849-] '. VARIABILITY. 37 



there were so many people there, that I for one hardly saw 

 anything of any one. Once again I thank you very cordially 

 for your kind present, and the pleasure it has given me, and 

 believe me, 



Ever most truly yours, 



C. DARWIN. 



P.S. I have quite forgotten to say how greatly interested I 

 was with your discussion on the statistics of animals : when 

 will Natural History be so perfect that such points as you 

 discuss will be perfectly known about any one animal ? 



C. Danvin to J. D. Hooker. 



Malvern, June 13 [1849]. 



. . . At last I am going to press with a small poor 

 first-fruit of my confounded Cirripedia, viz. the fossil ped- 

 unculate cirripedia. You ask what effect studying species 

 has had on my variation theories ; I do not think much I 

 have felt some difficulties more. On the other hand, I have 

 been struck (and probably unfairly from the class) with the 

 variability of every part in some slight degree of every 

 species. When the same organ is rigorously compared in 

 many individuals, I always find some slight variability, and 

 consequently that the diagnosis of species from minute 

 differences is always dangerous. I had thought the same 

 parts of the same species more resemble (than they do 

 anyhow in Cirripedia) objects cast in the same mould. 

 Systematic work would be easy were it not for this con- 

 founded variation, which, however, is pleasant to me as 

 a speculatist, though odious to me as a systematist. Your 

 remarks on the distinctness (so unpleasant to me) of the 

 Himalayan Rubi, willows, &c., compared with those of 

 northern [Europe?], &c., are very interesting; if my rude 

 species-sketch had any small share in leading you to these 



