Origin of Species Variorum

→ I believe, 1859 1860 1861 1866 1869

There is no evidence, 1872

→ in no 1859 1860 1861 1866 1869

of the existence of any 1872

→ If, for instance, 1859 1860 1861

If 1866 1869 1872

→ which stand in direct competition 1859 1860 1861

after having long competed 1866 1869 1872

→ migrate in 1859 1860 1861

in their old home, were to migrate in 1866 1869 1872

→ modified. 1859 1860

or at all modified. 1861 1866 1869 1872

and even

families,

families

are confined to the same areas, as is so commonly and notoriously the case.

→I believe, as was remarked in the last chapter, →in no law of necessary development. As the variability of each species is an independent property, and will be taken advantage of by natural selection, only so far as it profits

each

the

individual in its complex struggle for life, so the

amount

degree

of modification in different species will be no uniform quantity. →If, for instance, a number of species, →which stand in direct competition with each

other

other,

→migrate in a body into a new and afterwards isolated country, they

would

will

be little liable to modification; for neither migration nor isolation in themselves

can effect

effect

can do

anything. These principles come into play only by bringing organisms into new relations with each other, and in a lesser degree with the surrounding physical conditions. As we have seen in the last chapter that some forms have retained nearly the same character from an enormously remote geological period, so certain species have migrated over vast spaces, and have not become greatly →modified.

According to

these views, it is

obvious

obvious,

that the several species of the same genus, though inhabiting the most distant quarters of the world, must originally have proceeded from the same source, as they

are

have

descended from the same progenitor. In the case of those species, which have undergone during whole geological periods

~~but~~

but

little modification, there is not much difficulty in believing that they

~~may~~

may

have migrated from the same region; for during the vast geographical and climatal changes which

~~will~~

will

have supervened since ancient times, almost any amount of migration is possible. But in many other cases, in which we have reason to

believ

believe

that the species of a genus have been produced within comparatively recent times, there is great difficulty on this head. It