Origin of Species Variorum

→ which have suffered much extinction; but 1861 1866 1869 1872

but 1859 1860

→ OMIT 1860 1861 1866 1869 1872

as is proclaimed by the canon, "Natura non facit saltum," 1859

→ of 1859 1860 1861 1866 1869

in the same community of 1872

→ in the same community of ants; 1859 1860 1861 1866

ants in the same community; 1869

ants; 1872

→ trees 1859 1860 1861

distinct trees 1866 1869

distinct kinds of trees 1872

→ are crossed reciprocally; 1859 1860 1861

are crossed reciprocally,— 1866

reciprocally,— 1869 1872

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

Analogy from the consideration of dimorphic and trimorphic plants clearly leads to the same conclusion, for when the forms are illegitimately united, they yield few or no seed, and their offspring are more or less sterile; and these forms belong to the same undoubted species, and differ from each other in no respect except in their reproductive organs and functions.

→ has been asserted by so many authors to be universal, this cannot 1861 1866 1869 1872

cannot 1859 1860

→ correct after the facts given on the authority of Gärtner and Kölreuter. 1861 1866 1869

as universal; nor is their very general fertility surprising when we remember that it is not likely that either their constitutions or their reproductive systems should have been profoundly modified. 1859 1860

as quite correct after the facts given on the high authority of Gärtner and Kölreuter. 1872

→ Nor is the very general fertility of varieties, when crossed, surprising, when we remember that it is not likely that either their constitutions or their reproductive systems should 1861

Moreover, most of the varieties which 1859 1860 1866 1869

Most of the varieties which 1872

→ profoundly modified. Moreover, most of the varieties which 1861

experimentised on 1859 1860

experimented on 1866 1869 1872

→ experimented on have been produced 1861

produced 1859 1860 1866 1869 1872

→ (I do not mean mere confinement) apparently 1860 1861

apparently 1859

(I do not mean mere confinement) almost certainly 1866 1869 1872

→ sterility, 1859 1860 1861 1866 1869

that sterility which, judging from analogy, would have affected the parent-species if intercrossed, 1872

It is, no doubt, extremely difficult even to conjecture by what gradations many structures have been perfected, more especially amongst broken and failing groups of organic

beings;

beings,

→which have suffered much extinction; but we see so many strange gradations in nature, →OMIT that we ought to be extremely cautious in saying that any organ or instinct, or

the

any

whole

structure,

being,

could not have arrived at its present state by many graduated steps. There are, it must be admitted, cases of special difficulty

opposed to

the theory of natural selection; and one of the most curious of these is the existence →of two or three defined castes of workers or sterile

female

females

→in the same community of ants; but I have attempted to show how

this

these

difficulty

difficulties

can be mastered.

With respect to the almost universal sterility of species when first crossed, which forms so remarkable a contrast with the almost universal fertility of varieties when crossed, I must refer the reader to the recapitulation of the facts given at the end of the

ninth

eighth

chapter, which seem to me conclusively to show that this sterility is no more a special endowment than is the incapacity of two →trees to be grafted

together,

together;

but that it is incidental on

~~constitutional~~

constitutional

differences

confined to

the reproductive systems of the intercrossed species. We see the truth of this conclusion in the vast difference in the

results

result,

of crossing

when

the same two species →are crossed reciprocally; that is, when one species is first used as the father and then as the

mother:

mother.

↑

The

Although the

fertility of varieties when intercrossed and of their mongrel offspring →has been asserted by so many authors to be universal, this cannot be considered →correct after the facts given on the authority of Gärtner and Kölreuter. →Nor is the very general fertility of varieties, when crossed, surprising, when we remember that it is not likely that either their constitutions or their reproductive systems should have been →profoundly modified. Moreover, most of the varieties which have been →experimented on have been produced under domestication; and as domestication →(I do not mean mere confinement) apparently tends to eliminate →sterility, we