502. LETTERS TO DARWIN AND OTHERS. [1863, 
but clear, and I think useful. I see no occasion for 
finding fault with him, except in his attempts now 
and then to direct a little odium against you, which is 
unhandsome, for his main points are those I hammered 
out in the “ Atlantic,” ete. ; indeed I see signs of his 
having read the same. But it is hardly fair of him, 
after expressing his complete conviction that where 
the operation of natural causes can be clearly traced, 
the implication of design, upon its appropriate evi- 
dence, is not thereby rendered less certain or less 
convincing, to go on to speak of derivation-doctrine in 
a way that implies the contrary. 
Of course we believers in real design make the 
most of your “frank” and natural terms, “ contri- 
vance, purpose,” etc., and pooh-pooh your endeavors 
to resolve such contrivances into necessary results of 
certain physical processes, and make fun of the race 
between long noses and long nectaries ! 
March 23. 
Dr. Wyman,! who is a sharp fellow, tells me that, 
on the authority of the historian Prescott, the Incas 
of Peru, for no one knows how long, married their 
sisters, to keep the perfect purity of the blood. 
Query: How did this strong case of close-breeding 
operate? Did they run out thereby? Wyman thinks 
there is no evidence of it. 
If it is true, and the Incas stood it for a long 
course of generations, you must look to it, for it will 
bear hard against your theory of the necessity of 
crossing. If they run out, you will have a good case. 
1 Dr. Jeffries Wyman. 
