Origin of Species Variorum

→ we 1859 1860 1861 1866

no instance is 1869 1872

→ no fact countenancing the belief that the child ever reverts to some one ancestor, 1859 1860 1861 1866

crossed descendants reverting to an ancestor of foreign blood, 1869 1872

→ with some distinct breed, 1859 1860 1861 1866

OMIT 1869 1872

→ with a distinct breed, 1859 1860 1861 1866

OMIT 1869 1872

→ are 1859 1860 1861 1866

of reversion are 1869 1872

→ in treatises 1859 1860

by those who have written 1861 1866

together by those who have written 1869 1872

→ it is difficult, perhaps impossible, to bring forward one case of the hybrid offspring of two animals clearly distinct being themselves 1859 1860 1861 1866 1869

hardly any cases have been ascertained with certainty of hybrids from two quite distinct species of animals being 1872

→ from 1859 1860 1861 1866 1869

in species. From 1872

→ I think there is some probability in this hypothesis, 1859 1860 1861

and of some other domestic animals, there is great probability in this hypothesis, 1866 1869

and of some other domestic animals, this conclusion is probably quite correct, 1872

→ together, though it is unsupported by a single experiment. 1859 1860 1861

to each other, though it is unsupported by a single experiment. 1866 1869

to each other. 1872

→ seems to me 1859 1860 1861 1866 1869

would be 1872

that each breed, even the purest, has within a

dozen,

dozen

or,

most

most,

within a

score,

score

of generations, been crossed by the

rock-pigeon;

rock-pigeon:

I say within a dozen or twenty generations, for →we

known

know

of →no fact countenancing the belief that the child ever reverts to some one ancestor, removed by a greater number of generations. In a breed which has been crossed only

once,

once

→with some distinct breed, the tendency to

revert

reversion

to any character derived from such

a cross

cross

will naturally become less and less, as in each succeeding generation there will be less of the foreign blood; but when there has been no

cross,

cross

→with a distinct breed, and there is a tendency in

the breed

both parents

to revert to a

character

character,

which

was

has been

lost during some former generation, this tendency, for all that we can see to the contrary, may be transmitted undiminished for an indefinite number of generations. These two

quite distinct

distinct

cases →are often confounded →in treatises on inheritance.

Lastly, the hybrids or mongrels from between all the

~~domestic~~

domestic

breeds of

the pigeon

pigeons

are perfectly

fertile,

fertile.

as I

can state

~~this~~

this

from my own observations, purposely

made,

made

on the most distinct breeds. Now, → it is difficult, perhaps impossible, to bring forward one case of the hybrid offspring of two animals clearly distinct being themselves perfectly fertile. Some authors believe that long-continued domestication eliminates this strong tendency to

sterility

sterility:

→from the history of the

dog,

dog

→I think there is some probability in this hypothesis, if applied to species closely related →together, though it is unsupported by a single experiment. But to extend

the hypothesis

so far as to suppose that species, aboriginally as distinct as carriers, tumblers, pouters, and fantails now are, should yield offspring perfectly

fertile

fertile,

inter se , →seems to me rash in the extreme.

From these several reasons, namely,

— the

the

improbability of man having formerly

made

got

seven or eight supposed