462 LETTERS TO DARWIN AND OTHERS. [1863, 
Again, in your last sentence. When you wnscien- 
tific people take up a scientific principle you are apt to 
make too much of it, to push it to conclusions beyond 
what is warranted by the facts. But, because a par- 
ticular race has persisted in Egypt, how do you know 
that it is the only race capable of perpetuating itself ? 
If there had been a large infusion of different peo- 
ple in Egypt, and if they had exterminated the old 
race, do you not suppose this would have established 
itself, perpetuated itself, and that its particular adap- 
tations to the climate would have been different from 
that of the present race? 
If you cut off all future immigration into North 
America, would the Indians resume possession of the 
country ? or else our descendants become a copper- 
colored race ? ; 
_Enough for the present. When you have cracked 
these nuts, send me, if you please, another sheet. 
Ever yours cordially, Asa Gray. 
_CampBrincE, July 6, 1863. 
Dear Brace, — Yours of 20th ult. came just as J. 
was off for New Haven and I getting ready to go to 
her aid. 
We came back only on Thursday, or rather Friday 
morning. My hands so full that I could not write to 
Darwin, to whom I owe a long letter, till to-night. I 
will now inclose your note. 
It would be very like a chemist to think that exter- 
nal influences will explain everything. » But I pre- 
sume he believes that peculiarities are heritable. If 
he does, then he thinks he can explain, or will be able 
to explain, the origination of variations. I cannot, 
that is, to any extent, and do not expect to. When 
VSS Piel od Bog PARTON se 
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