Origin of Species Variorum

→ no instance is 1869 1872

we 1859 1860 1861 1866

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

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

→ OMIT 1869 1872

with some distinct breed, 1859 1860 1861 1866

→ OMIT 1869 1872

with a distinct breed, 1859 1860 1861 1866

→ of reversion are 1869 1872

are 1859 1860 1861 1866

→ together by those who have written 1869 1872

in treatises 1859 1860

by those who have written 1861 1866

→ 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

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

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

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

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

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

to each other. 1872

is thus coloured and marked, so that in each separate breed there might be a tendency to revert to the very same colours and markings. Or, secondly, 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 →no instance is

know

known

of →crossed descendants reverting to an ancestor of foreign blood, removed by a greater number of generations. In a breed which has been crossed only

once

once,

→OMIT the tendency to

reversion

revert

to any character derived from such

cross

a 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,

→OMIT and there is a tendency in

both parents

the breed

to revert to a

character,

character

which

has been

was

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 →of reversion are often confounded →together by those who have written 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,

→and of some other domestic animals, there is great probability in this hypothesis, if applied to species closely related →to each other, 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