Origin of Species Variorum

→ forms having 1869

parent-forms having occasionally 1859 1860 1861 1866

forms have 1872

→ constitute 1869

will give to us 1859 1860 1861 1866

these constitute 1872

→ OMIT 1869 1872

on my theory 1859 1860 1861 1866

→ by 1859 1860 1861 1866 1869

as at present by 1872

→ or by one or two. 1869

but such richness in species, as I find after some investigation, does not commonly fall to the lot of aberrant genera. 1859 1860 1861 1866

or by two or three. 1872

→ forms which have been 1869 1872

failing groups 1859 1860 1861 1866

→ still preserved under unusually favourable conditions. 1869 1872

preserved by some unusual coincidence of favourable circumstances. 1859 1860 1861 1866

→ OMIT 1869 1872

of the bizcacha to Marsupials 1859 1860 1861 1866

→ must be due in accordance with our view 1869 1872

are due on my theory 1859 1860 1861 1866

→ from a common progenitor. 1869 1872

in common. 1859 1860 1861 1866

→ naturally have been more or less intermediate in character 1866 1869 1872

have had a character in some degree intermediate 1859 1860 1861

and intermediate →forms having transmitted to the present day descendants but little modified, →constitute our so-called osculant or aberrant

groups.

species.

The more aberrant any form is, the greater must be the number of connecting forms which →OMIT have been exterminated and utterly lost. And we have some evidence of aberrant

forms

groups

having suffered severely from extinction, for they are

generally

almost always

represented by extremely few species; and such species as do occur are generally very distinct from each other, which again implies extinction. The genera Ornithorhynchus and Lepidosiren, for example, would not have been less aberrant had each been represented by a dozen

species,

species

instead of →by a single

one;

one,

→or by one or two. We can, I think, account for this fact only by looking at aberrant

forms

groups

as →forms which have been conquered by more successful competitors, with a few members →still preserved under unusually favourable conditions.

Mr. Waterhouse has remarked that, when a member belonging to one group of animals exhibits an affinity to a quite distinct group, this affinity in most cases is general and not special: thus, according to Mr. Waterhouse, of all Rodents, the bizcacha is most nearly related to Marsupials; but in the points in which it approaches this order, its relations are general, and not to any one marsupial species more than to another. As

these

the

points of affinity →OMIT are believed to be real and not merely adaptive, they →must be due in accordance with our view to inheritance →from a common progenitor. Therefore we must suppose either that all Rodents, including the

biz- cacha,

bizcacha,

branched off from some

very

....

ancient Marsupial, which will →naturally have been more or less intermediate in character with respect to all existing Marsupials; or that both Rodents and Marsupials branched off from a common progenitor, and that both groups have since