Origin of Species Variorum

→ it can no longer be maintained that varieties when crossed are invariably quite fertile. From 1872

from 1859 1860 1861 1866

it cannot be maintained that varieties when crossed are invariably quite fertile;—from 1869

→ proved to be infertile 1866 1869 1872

infertile 1859 1860 1861

→ a species;— from man attending only 1872

species; from man selecting only 1859 1860 1861

a species; from man selecting only 1866

a species;—from man attending only to 1869

→ his 1866 1869 1872

the production of the most distinct 1859 1860 1861

→ such varieties not having been exposed for very long periods to uniform conditions of life;— from 1872

not wishing or being able to produce recondite and functional differences in the reproductive system; from 1859 1860 1861

not wishing or being able to produce recondite and functional differences in their reproductive systems; from 1866

such varieties not having been exposed for a very long period to uniform conditions of life;—from 1869

→ we may conclude that fertility does not constitute 1869 1872

and facts, I do not think that the very general fertility of varieties can be proved to be of universal occurrence, or to form 1859 1860

and facts, I do not think that the very general fertility of varieties can be proved either to be of universal occurrence, or to form 1861

and facts, I do not think that the fertility of varieties can be proved either to be of universal occurrence, or to form 1866

→ species when crossed. 1869 1872

species. 1859 1860 1861 1866

→ crossed species may safely be looked at, not as 1872

varieties does not seem to me sufficient to overthrow the view which I have taken with respect to the very general, but not invariable, sterility of first crosses and of hybrids, namely, that it is not 1859 1860

varieties, considering how entirely ignorant we are on the causes of both fertility and sterility, does not seem to me sufficient to overthrow the view taken with respect to the very general, but not invariable, sterility of first crosses between species and of their hybrids, namely, that it is not 1861 1866

crossed species may safely be looked at not as 1869

→ acquirement or endowment, but as 1869 1872

endowment, but is 1859 1860 1861 1866

→ changes of an unknown nature in their sexual elements. 1869 1872

slowly acquired modifications, more especially in the reproductive systems of the forms which are crossed. 1859 1860 1861

modifications, slowly impressed, by unknown means, on the reproductive systems of the parent-forms. 1866

→ compared , 1872

compared, 1859 1860

compared , 1861

compared, 1866 1869

→ in both cases is 1869 1872

is 1859 1860 1861 1866

→ instances of both 1869 1872

cases both of 1859 1860 1861 1866

of this one variety must have been in some manner and in some degree modified.

From these

facts;

facts

→it can no longer be maintained that varieties when crossed are invariably quite fertile. From the great difficulty of ascertaining the infertility of varieties in a state of nature, for a supposed

variety

variety,

if →proved to be infertile in any

degree

degree,

would

generally

almost universally

be ranked as →a species;— from man attending only

external

to external

characters in →his domestic varieties, and from →such varieties not having been exposed for very long periods to uniform conditions of life;— from these several considerations →we may conclude that fertility does not constitute a fundamental distinction between

them

varieties

and →species when crossed. The general

fertility

sterility

of →crossed species may safely be looked at, not as a special →acquirement or endowment, but as incidental on →changes of an unknown nature in their sexual elements.

Hybrids

and

Mongrels

→ compared ,

independently

their

fertility .—

fertility .

Independently of the question of fertility, the offspring of species

when crossed

....

and of varieties when crossed may be compared in several other respects. Gärtner, whose strong wish

was

it was

to draw a

marked

distinct

line

of distinction

....

between species and varieties, could find very

few

few,

and, as it seems to me, quite unimportant differences between the so-called hybrid offspring of species, and the so-called mongrel offspring of varieties. And, on the other hand, they agree most closely in

very

....

many important respects.

I shall here discuss this subject with extreme brevity. The most important distinction is, that in the first generation mongrels are more variable than hybrids; but Gärtner admits that hybrids from species which have long been cultivated are often variable in the first generation; and I have myself seen striking instances of this fact. Gärtner further admits that hybrids between very closely allied species are more variable than those from very distinct species; and this shows that the difference in the degree of variability graduates away. When mongrels and the more fertile hybrids are propagated for several

generations

generations,

an extreme amount of variability in

their

the

offspring →in both cases is

notori- ous;

notorious;

but some few →instances of both hybrids and mongrels long retaining

uniformity of

a uniform

character could be given. The variability, however, in the successive generations of mongrels is, perhaps, greater than in hybrids.

This greater variability

mongrels than

hybrids does not seem

to me

....

at all surprising. For the parents of mongrels are varieties, and mostly domestic varieties (very few experiments having been