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been used. The knowledge it implies could not be inherited; it must
needs come by experience. When a fowl eats gravel or sand, is it
probable that the fowl knows what the practice is for, or has any
notion at all about the matter? It has a craving for the gravel, that
is all. Nature is wise for it.

The ostrich is described by those who know it intimately as the most
stupid and witless of birds, and yet before leaving its eggs exposed
to the hot African sun, the parent bird knows enough to put a large
pinch of sand on the top of each of them, in order, it is said, to
shade and protect the germ, which always rises to the highest point of
the egg. This act certainly cannot be the result of knowledge, as we
use the term; the young ostrich does it as well as the old. It is the
inherited wisdom of the race, or instinct.

A sitting bird or fowl turns its eggs at regular intervals, which has
the effect of keeping the yolk from sticking to the shell. Is this act
the result of knowledge or of experience? It is again the result of
that untaught knowledge called instinct. Some kinds of eggs hatch in
two weeks, some in three, others in four. The mother bird has no
knowledge of this period. It is not important that she should have. If
the eggs are addled or sterile, she will often continue to sit beyond
the normal period. If the continuance of the species depended upon her
knowing the exact time required to hatch her eggs, as it depends upon
her having the incubating fever, of course she would know exactly, and
would never sit beyond the required period.

But what shall we say of Mrs. Annie Martin's story, in her "Home Life
on an Ostrich Farm," of the white-necked African crow that, in order
to feast upon the eggs of the ostrich, carries a stone high in the air
above them and breaks them by letting it fall? This looks like reason,
a knowledge of the relation of cause and effect. Mrs. Martin says the
crows break tortoise-shells in the same way, and have I not heard of
our own crows and gulls carrying clams and crabs into the air and
dropping them upon the rocks?

If Mrs. Martin's statements are literally true,--if she has not the
failing, so common among women observers, of letting her feeling and
her fancies color her observations,--then her story shows how the
pressure of hunger will develop the wit of a crow.

But the story goes one step beyond my credence. It virtually makes the
crow a tool-using animal, and Darwin knew o