Origin of Species Variorum

→ land than with those of the sea. 1869 1872

sea. 1859 1860 1861 1866

↑ 6 blocks not present in 1869 1872; present in 1859 1860 1861 1866

Dominant species spreading from any region might encounter still more dominant species, and then their triumphant course, or even their existence, would cease. We know not at all precisely what are all the conditions most favourable for the multiplication of new and dominant species; but we can, I think, clearly see that a number of individuals, from giving a better chance of the appearance of favourable variations, and that severe competition with many already existing forms, would be highly favourable, as would be the power of spreading into new territories. A certain amount of isolation, recurring at long intervals of time, would probably be also favourable, as before explained. One quarter of the world may have been most favourable for the production of new and dominant species on the land, and another for those in the waters of the sea. If two great regions had been for a long period favourably circumstanced in an equal degree, whenever their inhabitants met, the battle would be prolonged and severe; and some from one birthplace and some from the other might be victorious. But in the course of time, the forms dominant in the highest degree, wherever produced, would tend everywhere to prevail.

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

As they prevailed, they would cause the extinction of other and inferior forms; and as these inferior forms would be allied in groups by inheritance, whole groups would tend slowly to disappear; though here and there a single member might long be enabled to survive.

→ their having 1869 1872

inheritance, and to having already 1859 1860 1861

inheritance and to having already 1866

→ already dominant parents, as well as 1869 1872

parents or 1859 1860 1861 1866

→ new forms. 1869 1872

new species. 1859 1860 1861

other new forms. 1866

→ OMIT 1869 1872

in both ways will 1859 1860 1861

will 1866

→ correspond both in their first appearance and final disappearance. 1869 1872

correspond. 1859 1860 1861

correspond in their first appearance and final disappearance. 1866

→ rich in fossils, were 1861 1866 1869 1872

were 1859 1860

→ as far as fossils are concerned, occurred 1869 1872

occurred 1859 1860 1861 1866

degree of

parallel

parallelism

succession

....

in the

productions

succession

of the

land than

productions

of the →land than with those of the sea. ↑ ↑

Thus, as it seems to me, the parallel, and, taken in a large sense, simultaneous, succession of the same forms of life throughout the world, accords well with the principle of new species having been formed by dominant species spreading widely and varying; the new species thus produced being themselves

dominant

dominant,

owing to →their having had some advantage over their →already dominant parents, as well as over other

species;

species,

these

and

again spreading, varying, and producing →new forms. The

forms

old forms

which are beaten and which yield their places to the new and victorious forms, will generally be allied in groups, from inheriting some inferiority in common; and

therefore

therefore,

as new and improved groups spread throughout the world, old groups

will

....

disappear from the world; and the succession of forms →OMIT everywhere

tend

tends

to →correspond both in their first appearance and final disappearance.

There is one other remark connected with this subject worth making. I have given my reasons for believing that

all

most of

our

greater

great

fossiliferous

....

formations

formations,

→rich in fossils, were deposited during periods of subsidence; and that blank intervals of vast

duration

duration,

→as far as fossils are concerned, occurred during the periods when the bed of the sea was either stationary or rising, and likewise when sediment was not thrown down quickly enough to embed and preserve organic remains. During these long and blank intervals I suppose that the inhabitants of each region underwent a considerable amount of modification and extinction, and that there was much migration from other parts of the world. As we have reason to believe that large areas are affected by the same movement, it is probable that strictly contemporaneous formations have often been accumulated over very wide spaces in the same quarter of the world; but we are

far

very far

from having any right to conclude that this has invariably been the case, and that large areas have

inva- riably

invariably

been affected by the same movements. When two formations have been deposited in two regions during nearly, but not

exactly

exactly,

the same period, we should find in both, from the causes explained in the foregoing paragraphs, the same general succession in the forms of life; but the species would not exactly correspond; for there will have been a little more time in the one region than in the other for modification, extinction, and immigration.

I suspect that cases of this nature

have occurred

occur

in Europe. Mr. Prestwich, in his admirable Memoirs on the eocene deposits of England and France, is able to draw a close general parallelism between the successive stages in the two countries; but when he