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I can see no 1859 1860 1861 1866
there is no real 1869 1872

slight modifications of instinct to any extent, 1859 1860 1861 1866
to any extent slight modifications of instinct which are 1869 1872

has 1859 1860 1861 1866
can be shown to have 1869 1872

but that each 1859 1860 1861 1866
though 1869 1872

male wrens (Troglodytes) of North America, build "cock-nests," to roost in, like 1859 1860
Hornbills of Africa and India have the same extraordinary instinct of plastering up and imprisoning 1861 1866 1869 1872

of our distinct 1859 1860
in a hole in a tree, with only a small hole left in the plaster through which the males feed them and their young when hatched: how it is that the male wrens (Troglodytes) of North America, build "cock-nests," to roost in, like the males of our distinct 1861
in a hole in a tree, with only a small hole left in the plaster through which the males feed them and their young when hatched: how it is that the male wrens (Troglodytes) of North America build "cock-nests," to roost in, like the males of our 1866
in a hole in a tree, with only a small hole left in the plaster through which the males feed them and the young when hatched: how it is that the male wrens (Troglodytes) of North America build "cock-nests," to roost in, like the males of our 1869
in a hole in a tree, with only a small hole left in the plaster through which the males feed them and their young when hatched; how it is that the male wrens (Troglodytes) of North America build "cock-nests," to roost in, like the males of our 1872

to show that the mental qualities of our domestic animals vary, and that the variations are inherited. Still more briefly I have attempted to show that
in-
....
stincts
instincts
vary slightly in a state of nature. No one will dispute that instincts are of the highest importance to each animal.
There- fore
Therefore
I can see no difficulty, under changing conditions of life, in natural selection accumulating slight modifications of instinct to any extent, in any
way useful.
useful direction.
In
many
some
cases habit or use and disuse have probably come into play. I do not pretend that the facts given in this chapter strengthen in any great degree my theory; but none of the cases of difficulty, to the best of my judgment, annihilate it. On the other hand, the fact that instincts are not always absolutely perfect and are liable to mistakes;— that no instinct has been produced for the
exclusive
exclusive
good of other animals, but that each
animals
animal
take
takes
advantage of the instincts of others;— that the
cannon
canon
in natural history, of
"natura
"Natura
non facit
saltum"
saltum,"
is applicable to instincts as well as to corporeal structure, and is plainly explicable on the foregoing views, but is otherwise inexplicable,— all tend to corroborate the theory of natural selection.
This theory
is
is,
also
also,
strengthened by some few other facts in regard to instincts; as by that common case of closely allied, but
certainly
certainly
distinct, species, when inhabiting distant parts of the world and living under considerably different conditions of life, yet often retaining nearly the same instincts. For instance, we can
understand,
understand
on the principle of inheritance, how it is that the thrush of
tropical South
South
America lines its nest with mud, in the same peculiar manner as does our British
thrush;
thrush:
how it is that the male wrens (Troglodytes) of North America, build "cock-nests," to roost in, like the
females
males
of our distinct Kitty-wrens,— a habit wholly unlike that of