168 EVOLUTION [CHAP. Ill 



Letter 112 which our domestic pigeon would cross that is, if several 

 excessively close geographical races of C. livia, which hardly 

 any ornithologist looks at as true species, be all grouped under 

 C. livia. 1 



I am writing higgledy-piggledy, as I re-read your letter. 

 I thought that my letter had been much wilder than yours. 

 I quite feel the comfort of writing when one may " alter one's 

 speculations the day after." It is beyond my knowledge to 

 weigh ranks of birds and monotremes ; in the respiratory and 

 circulatory system and muscular energy I believe birds are 

 ahead of all mammals. 



I knew that you must have known about New Guinea ; 

 but in writing to you I never make myself civil ! 



After treating some half-dozen or dozen domestic animals 

 in the same manner as I treat dogs, I intended to have a 

 chapter of conclusions. But Heaven knows when I shall 

 finish : I get on very slowly. You would be surprised how 

 long it took me to pick out what seemed useful about dogs 

 out of multitudes of details. 



I see the force of your remark about more isolated races 

 of man in old times, and therefore more in number. It seems 

 to me difficult to weigh probabilities. Perhaps so, if you 

 refer to very slight differences in the races : to make great 

 differences much time would be required, and then, even at 

 the earliest period I should have expected one race to have 

 spread, conquered, and exterminated the others. 



With respect to Falconer's series of Elephants, 2 I think 

 the case could be answered better than I have done in the 

 Origin, p. 334- 3 All these new discoveries show how imperfect 



1 Columba lima, the Rock-pigeon. " We may conclude with con- 

 fidence that all the domestic races, notwithstanding their great amount 

 of difference, are descended from the Columba livia, including under this 

 name certain wild races " (op. cit., Vol. I., p. 223). 



2 In 1837 Dr. Falconer and Sir Proby Cautley collected a large 

 number of fossil remains from the Siwalik Hills. Falconer and Cautley, 

 Fauna Antiqua Sivalensis, 1845-49. 



3 Origin of Species, Ed. I., p. 334. " It is no real objection to the 

 truth of the statement that the fauna of each period as a whole is nearly 

 intermediate in character between the preceding and succeeding faunas, 

 that certain genera offer exceptions to the rule. For instance, mastodons 

 and elephants, when arranged by Dr. Falconer in two series, first accord- 

 ing to their mutual affinities and then according to their periods of 



