LIFE OF JAMES DWIGHT DANA 



On the Origin of Species 



ASA GRAY TO DANA 



"CAMBRIDGE, December 13, 1856. 



' The right way of bringing a series of pretty interest- 

 ing general questions towards settlement is perhaps in 

 hand (though I do not expect myself to bring anything 

 important to bear upon it), namely, for a number of totally 

 independent naturalists, of widely different pursuits and 

 antecedents, to environ it on all sides, work towards a 

 common centre, but each to work independently. Such 

 men as Darwin, Dr. Hooker, De Candolle, Agassiz, and 

 yourself most of them with no theory they are bound 

 to support ought only to bring out some good results. 

 And the less each one is influenced by the others' mode 

 of viewing things the better. For my part, in respect to 

 the bearings of the distribution of plants, etc., I am de- 

 termined to know no theory, but to see what the facts 

 tend to show, when fairly treated. 



" On the subject of species, their nature, distribution, 

 what system in natural history is, etc., certain inferences 

 are slowly settling 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 bias, 

 thanks, partly, to the fact that I can think of and investi- 

 gate such matters only now and then, and in a very 

 desultory way. 



" I cannot say that I believe in centres of radiation for 

 groups of species. From Darwin's questions to me I 

 think I perceive some of the grounds on which he would 

 maintain it. One is alluded to on page 77 of the January 

 number [of Silliman 's Journal^, but I am not clear that 

 they are not just as susceptible of other interpretation. 



' But as to a centre of radiation of each separate species, 

 I must say that I have a bias that way. You seem to have 

 also, and you can best judge whether this, combined with 

 geological considerations, would not involve centres of 

 radiation for groups of species as well, to a certain extent. 

 Would not the fact that the members of peculiar groups 

 (in Vegetable Kingdom) are to a great extent localized 

 favor that view ? 



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