Origin of Species Variorum

→ can, indeed, hardly be doubted. 1869 1872

I am inclined to believe in its truth, although it rests on no direct evidence. 1859 1860 1861

I have hardly any doubt of its truth, although it rests on no direct evidence. 1866

→ almost certain that 1866 1869 1872

that 1859 1860 1861

→ I have lately acquired decisive evidence that the crossed offspring from the Indian humped and common 1866 1869 1872

there is reason to believe that our European and the humped Indian 1859 1860 1861

→ inter se perfectly fertile; and from the observations by Rütimeyer on their important osteological differences, as well as from those 1872

quite fertile together; but from facts communicated to me 1859 1860 1861

inter se perfectly fertile; and from the observations by Rütimeyer on their important osteological differences, as well as from those 1866 1869

→ on their differences in habits, voice, constitution, &c., these two forms 1866 1869 1872

I think they 1859 1860 1861

→ good and distinct species. 1872

distinct species. 1859 1860 1861

good and distinct species—as good as any in the world. 1866

good and distinct species as any in the world. 1869

→ We must, therefore, either give up the belief 1872

On this view 1859 1860 1861 1866

According to this view 1869

→ universal sterility of species when crossed; or 1872

origin of many of our domestic animals, 1859 1860 1861 1866

origin of many domestic animals, 1869

→ OMIT 1872

either give up the belief of the almost universal sterility of distinct species of animals when crossed; or we must 1859 1860 1861 1866 1869

→ this sterility in animals, 1872

sterility, 1859 1860 1861 1866 1869

→ laws 1872

circumstances and rules 1859 1860 1861 1866 1869

→ drawn up chiefly 1872

chiefly drawn up 1859 1860 1861 1866 1869

the most probable, and →can, indeed, hardly be doubted.

I believe,

It is,

for instance, →almost certain that our dogs

have

are

descended from several wild stocks; yet, with perhaps the exception of certain indigenous domestic dogs of South America, all are quite fertile together;

and

but

analogy makes me greatly doubt, whether the several aboriginal species would at first have freely bred together and have produced quite fertile hybrids. So again →I have lately acquired decisive evidence that the crossed offspring from the Indian humped and common cattle are → inter se perfectly fertile; and from the observations by Rütimeyer on their important osteological differences, as well as from those by Mr.

Blyth,

Blyth

→on their differences in habits, voice, constitution, &c., these two forms must be

considered

regarded

as →good and distinct species. The same remarks may be extended to the two chief races of the pig. →We must, therefore, either give up the belief of the →universal sterility of species when crossed; or we must →OMIT look at →this sterility in animals, not as an indelible characteristic, but as one capable of being removed by domestication.

Finally,

looking to

considering

all the ascertained facts on the intercrossing of plants and animals, it may be

con- cluded

concluded

that some degree of sterility, both in first crosses and in hybrids, is an extremely general result; but that it cannot, under our present state of knowledge, be considered as absolutely universal.

Laws

governing

the

Sterility

first

Crosses

and

Hybrids .—

Hybrids .

We will now consider a little more in detail the →laws governing the sterility of first crosses and of hybrids. Our chief object will be to see whether or not

the rules

these laws

indicate that species have

specially been

been specially

endowed with this quality, in order to prevent their crossing and blending together in utter confusion. The following

rules and

....

conclusions are →drawn up chiefly from

Gärtners

Gärtner's

admirable work on the hybridisation of plants. I have taken much pains to ascertain how far

the

they

rules

....

apply to animals,

and

and,

considering how scanty our knowledge is in regard to hybrid animals, I have been surprised to find how generally the same rules apply to both kingdoms.

It has been already remarked, that the degree of fertility, both of first crosses and of hybrids, graduates from zero to perfect fertility. It is surprising in how many curious ways this gradation can be

shown

shown;

to exist;

....

but only the barest outline of the facts can here be given. When pollen from a plant of one family is placed on the stigma of a plant of a distinct family, it exerts

more influence than so much inorganic dust. From this absolute zero of