Asa Gray. 197 



explain to Dr. Gray with detail, under six heads, the prominent 

 facts and arguments in the theory of "Natural Selection," 

 which he says is the " title of his book." This letter is the 

 first exposition that Darwin had made of his theory, and hence 

 it has proved to have great documentary value. 



A letter which the writer received from Gray in the inter- 

 val between Darwin's two letters, dated December 13, 1856, 

 shows well the state of his mind at that time. He says : " On 

 the subject of species, their nature, distribution, what system in 

 Natural History is, etc., etc., certain inferences are slowly set- 

 tling themselves in my mind or taking shape ; but, on some of 

 the most vexed questions, I have as yet no opinion whatever, 

 and no very strong Mas, thanks partly to the fact, that I can 

 think of and investigate such matters only now and then, and 

 in a very desultory way."* 



In a letter of a year later, subsequent in date to Darwin's 

 letter, Gray wrote me with reference to my paper on " Species " 

 read at the meeting of the American Association in August, 

 1857— which paper may be taken, perhaps, as a culmination of 

 the past, just as the new future was to make its appearance — 

 pointing out to me the fatal objection to my argument. 



His words (dated November 7th) are worth quoting : " Tak- 

 ing the cue of species, if I may so say, from the inorganic, you 

 develop the subject to great advantage for your view, and all 

 you say must have great weight in ' reasoning from the gen- . 

 eral.' But in reasoning from, inorganic species to organic 

 species, and in making it tell where you want it, and for what 

 you want it to tell, you must be sure that you are using 

 the word species in the same sense in the two ; that the 

 one is really the equivalent of the other. That is what 

 I am not yet convinced of ; and so to me the argument 

 comes only with the force of an analogy, whereas I sup- 

 pose you want it to come as demonstration. Yery likely 

 you could convince me that there is no fallacy in reason- 

 ing from the one to the other to the extent you do. But all 



* Gray has some important observations on the bearing of hybridization on 

 variation, in a review of Hooker's Flora Indica in the number of this Journal for 

 January, 1856, (xxi, 134). 



Am. Jour. Sci.— Third Series, Vol. XXXV, No. 207.— March, 1888. 

 12 



