WAYS OF NATURE 
We are not warranted in attributing to any wild, 
untrained animal a degree of intelligence that its 
forbears could not have possessed. The animals 
for the most part act upon inherited knowledge, that 
is, knowledge that does not depend upon instruction 
or experience. For instance, the red squirrels near 
me seem to know that chestnut-burs will open if cut 
from the tree and allowed to lie upon the ground. At 
least, they act upon this theory. I do not suppose 
this fact or knowledge lies in the squirrel’s mind as 
it would in that of a man — as a deduction from 
facts of experience or of observation. The squirrel 
cuts off the chestnuts because he is hungry for them, 
and because his ancestors for long generations have 
cut them off in the same way. That the air or sun 
will cause the burs to open is a bit of knowledge that 
I do not suppose he possesses in the sense in which 
we possess it: he is in a hurry for the nuts, and 
does not by any means always wait for the burs to 
open; he frequently chips them up and eats the pale 
nuts. 
The same squirrel will bite into the limbs of a 
maple tree in spring and suck the sap. What does 
he know about maple trees and the spring flow of 
sap? Nothing as a mental concept, as a bit of con- 
crete knowledge. He often finds the sap flowing 
from a crack or other wound in the limbs of a maple, 
and he sips it and likes it. Then he sinks his teeth 
into the limb, as his forbears undoubtedly did. 
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