Origin of Species Variorum

→ been subjected to 1872

varied and become 1859 1860 1861 1866 1869

→ conditions, or which have slightly varied, give 1872

give 1859 1860 1861 1866 1869

→ OMIT 1872

that greater changes, or changes of a particular nature, often render 1859 1860 1861 1866 1869

→ long habituated to certain uniform conditions under a state of nature, when subjected, as under confinement, to a considerable change in their conditions, very frequently are rendered more or less 1872

in some degree 1859 1860 1861 1866 1869

→ we know that a 1872

that greater crosses, that is 1859 1860 1861 1866 1869

→ two forms, that 1872

males and females which 1859 1860 1861 1866 1869

→ am fully persuaded 1872

cannot persuade myself 1859 1860 1861 1866 1869

→ double parallelism is by no means 1872

parallelism is 1859 1860 1861 1866 1869

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

Both series of facts seem to be connected together by some common but unknown bond, which is essentially related to the principle of life.

→ the two having 1872

both with 1866 1869

→ the three forms possess 1872

there are 1866 1869

Hence it seems that, on the one hand, slight changes in the conditions of life benefit all organic beings, and on the other hand, that slight crosses, that is crosses between the males and females of the same

species

species,

which have →been subjected to slightly

different,

different

→conditions, or which have slightly varied, give vigour and fertility to the offspring.

But

But,

as we

have

seen

seen,

→OMIT organic beings →long habituated to certain uniform conditions under a state of nature, when subjected, as under confinement, to a considerable change in their conditions, very frequently are rendered more or less sterile; and →we know that a

crosses

cross

between →two forms, that have become widely or specifically different, produce hybrids which are

generally sterile

almost always

in some

degree.

degree sterile.

I →am fully persuaded that this →double parallelism is by no means an accident or an illusion. He who is able to explain why the elephant and a multitude of other animals are incapable of breeding when kept under only partial confinement in their native country, will be able to explain the primary cause of hybrids being so generally sterile. He will at the same time be able to explain how it is that the races of some of our domesticated animals, which have often been subjected to new and not uniform conditions, are quite fertile together, although they are descended from distinct species, which would probably have been sterile if aboriginally crossed. The above two parallel series of facts seem to be connected together by some common but unknown bond, which is essentially related to the principle of life; this principle, according to Mr. Herbert Spencer, being that life depends on, or consists in, the incessant action and reaction of various forces, which, as throughout nature, are always tending towards an equilibrium; and when this tendency is slightly disturbed by any change, the vital forces gain in power. ↑

Reciprocal Dimorphism and Trimorphism .

This subject may be here briefly discussed, and will be found to throw

considerable

some

light on hybridism. Several plants belonging to distinct orders present two forms,

existing together

which exist

in about equal

numbers,

numbers

which

and which

differ in no respect except in their reproductive organs; one form having a long pistil with short stamens, the other a short pistil with long stamens; →the two having differently sized pollen-grains. With trimorphic plants there are three forms likewise differing in the lengths of their pistils and stamens, in the size and colour of the pollen-grains, and in some other respects; and as in each of the three forms there are two sets of stamens, →the three forms possess altogether six sets of stamens and three kinds of pistils. These organs are so proportioned in length to each other,