Origin of Species Variorum

→ the production of the most distinct 1859 1860 1861

his 1866 1869 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

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

we may conclude that fertility does not constitute 1869 1872

→ species. 1859 1860 1861 1866

species when crossed. 1869 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

crossed species may safely be looked at, not as 1872

→ endowment, but is 1859 1860 1861 1866

acquirement or endowment, but as 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

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

→ compared, 1859 1860

compared , 1861

compared, 1866 1869

compared , 1872

to external

external

characters in →the production of the most distinct domestic varieties, and from →not wishing or being able to produce recondite and functional differences in the reproductive system; from these several considerations →and facts, I do not think that the very general fertility of varieties can be proved to be of universal occurrence, or to form a fundamental distinction between

them

varieties

and →species. The general

sterility

fertility

of →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 a special →endowment, but is incidental on →slowly acquired modifications, more especially in the reproductive systems of the forms which are crossed.

Hybrids

and

Mongrels

→ compared,

independently

their

fertility .

fertility .—

Independently of the question of fertility, the offspring of species

~~when crossed~~

when crossed

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

it was

was

to draw a

distinct

marked

line

~~of distinction~~

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~~

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