Origin of Species Variorum

→ them becoming inarched 1859 1860 1861 1866

their inarching 1869 1872

→ between pure species, which have their reproductive systems perfect, seems to depend on several circumstances; in some cases largely on the early death of the embryo. 1859 1860 1861

and of their hybrid progeny has not, as far as we can judge, been increased through natural selection so as to attain that high degree which is universal with species when rendered widely distinct. 1866

and of their hybrid progeny has not, as far as we can judge, been acquired through natural selection. 1869

and of their hybrid progeny has not been acquired through natural selection. In the case of first crosses it seems to depend on several circumstances; in some instances in chief part on the early death of the embryo. 1872

↑ 1 blocks not present in 1859 1860 1861 1872; present in 1866 1869

With first crosses between pure species, in which the reproductive system is in a perfect condition, the sterility seems to depend on several circumstances; in some cases largely on the early death of the embryo, but this apparently depends on some imperfection in the original act of impregnation.

→ The sterility of hybrids, which have their reproductive systems imperfect, and which have had this system and their 1859 1860 1861

With hybrids, in which the reproductive system is in an imperfect condition, and in which this system as well as the 1866

In the case of hybrids, it perhaps depends on their 1869

→ disturbed 1859 1860 1861

has been disturbed 1866

having been disturbed 1869

→ species, seems 1859 1860 1861

forms, the sterility apparently is 1866

forms; the sterility being 1869

→ the crossing of forms only slightly different is favourable to 1859 1860 1861

the crossing of forms only slightly differentiated favours 1866

first, the crossing of forms only slightly differentiated favours 1869

firstly, slight changes in the conditions of life add to 1872

→ their offspring; and that slight changes in the 1859 1860 1861 1866

their offspring, whilst close interbreeding is injurious; and secondly, that slight changes in the 1869

all organic beings; and secondly, that the crossing of forms, which have been exposed to slightly different 1872

→ are apparently favourable to the 1859 1860 1861

apparently add to the 1866 1869

or which have varied, favours the size, 1872

→ all organic beings. 1859 1860 1861 1866

all organic beings, whilst greater changes are often injurious. 1869

their offspring. 1872

→ generally correspond, though 1859 1860 1861

in most cases correspond, even if 1872

→ of some kind 1859 1860 1861

OMIT 1872

→ from it, and 1860 1861

and 1859 1872

→ attempts to express 1859 1860 1861

includes resemblances of 1872

→ quite uni- versally, 1860

quite universally, 1859

as is so often falsely stated, universally 1861

as is so often stated, universally 1866

as is so often stated, invariably 1869 1872

somewhat analogous degrees of difficulty in being grafted together in order to prevent →them becoming inarched in our forests.

The sterility of first crosses →between pure species, which have their reproductive systems perfect, seems to depend on several circumstances; in some cases largely on the early death of the embryo. ↑ →The sterility of hybrids, which have their reproductive systems imperfect, and which have had this system and their whole organisation →disturbed by being compounded

from

two distinct →species, seems closely allied to that

~~sterility~~

sterility

which so frequently affects pure species, when

exposed to

their

unnatural

natural

conditions of

life.

~~have~~

~~been~~

~~disturbed.~~

This view is

strongly supported

supported

by a parallelism of another

kind:—

kind:

kind;—

namely,

that,

that

→the crossing of forms only slightly different is favourable to the vigour and fertility of →their offspring; and that slight changes in the conditions of life →are apparently favourable to the

vigour,

vigour

and fertility of →all organic beings. It is not surprising that the

~~degree of~~

degree of

difficulty in

crossing any

uniting

two species, and the

sterility

degree

~~sterility of~~

sterility of

their

hybrid-offspring,

hybrid offspring,

hybrid-offspring

should →generally correspond, though due to distinct causes; for both depend on the amount of difference →of some kind between the species which are crossed. Nor is it surprising that the facility of effecting a first cross,

and the

the

fertility of the hybrids

produced,

thus produced,

produced

→from it, and the capacity of being grafted together— though this latter capacity evidently depends on widely different circumstances— should all run, to a certain extent, parallel with the systematic affinity of the forms

~~which are~~

which are

subjected to experiment; for systematic affinity →attempts to express all

kinds.

~~resemblance~~

~~between~~

~~all~~

~~species.~~

First crosses between forms known to be varieties, or sufficiently alike to be considered as varieties, and their mongrel offspring, are very generally, but

not,

not

→quite uni- versally,