See page in:
1859
1860
1861
1866
1869
1872

Compare with:
1859
1860
1861
1866
1872

but little improved structures, 1869 1872
little improved organisation 1861 1866

by having become at each stage 1869 1872
though becoming under each grade 1861 1866

generally within the same 1869
within a confined 1859 1860 1861 1866
within the same 1872

are the 1869 1872
will generally be 1859 1860 1861
generally are the 1866

This fact is perfectly compatible with numerous beings still retaining
a
....
simple and but little improved structures, fitted for simple conditions of life; it is likewise compatible with some forms having retrograded in organisation, by having become at each stage of descent better fitted for
their changed
new
changed
and degraded habits of life. Lastly, the
law
wonderful law
of the long endurance of allied forms on the same continent,— of marsupials in Australia, of edentata in America, and other such cases,— is intelligible, for generally within the same
country
country,
the
recent
existing
and the extinct will
naturally
....
be
allied
closely allied
by descent.
Looking to geographical distribution, if we admit that there has been during the long course of ages much migration from one part of the world to another, owing to former climatal and geographical changes and to the many occasional and unknown means of dispersal, then we can understand, on the theory of descent with modification, most of the great leading facts in Distribution. We can see why there should be so striking a parallelism in the distribution of organic beings throughout space, and in their geological succession throughout time; for in both cases the beings have been connected by the bond of ordinary generation, and the means of modification have been the same. We see the full meaning of the wonderful fact, which
must have
has
struck every traveller, namely, that on the same continent, under the most diverse conditions, under heat and cold, on mountain and lowland, on deserts and marshes, most of the inhabitants within each great class are plainly related; for they are the descendants of the same progenitors and early colonists. On this same principle of former migration, combined in most cases with modification, we can understand, by the aid of the Glacial period, the identity of some few plants, and the close