Origin of Species Variorum

→ OMIT 1869 1872

strictly correspond with the succession of our geological formations; so that between each two consecutive formations, the forms of life have seldom changed in exactly 1859 1860 1861 1866

→ in each successive so-called formation. 1869 1872

degree. 1859 1860 1861 1866

→ which includes 1869 1872

I believe in 1859 1860 1861 1866

→ slow, and will generally affect only a few species at the same time; 1869 1872

slow. 1859 1860 1861 1866

→ variations or individual differences as may arise will be accumulated through 1869 1872

variability be taken advantage of by 1859 1860 1861 1866

→ in 1869 1872

and whether the variations be accumulated to 1859 1860 1861 1866

→ of 1859 1860 1861 1869 1872

thus causing a greater or lesser amount of 1866

→ permanent modification, will 1869 1872

modification in the varying species, 1859 1860 1861 1866

→ OMIT 1869 1872

rate of breeding, on the 1859 1860 1861 1866

→ OMIT 1869 1872

and more especially 1859 1860 1861 1866

→ new colonists, and on the nature of the 1869 1872

the 1859 1860 1861 1866

→ in a less degree. 1869 1872

less. 1859 1860 1861 1866

→ find similar relations between the existing inhabitants of distinct countries; 1872

see the same fact in geographical distribution; 1859 1860 1861 1866

find similar relations between the inhabitants of distinct countries; 1869

→ from the 1869 1872

on that of the many 1859 1860 1861 1866

seem to

change

have changed

at a quicker rate than those of the sea, of which a striking instance has

lately

....

been observed in Switzerland. There is some reason to believe that

organisms,

organisms

considered

....

high in the

scale

scale,

of nature,

....

change more quickly than those that are low: though there are exceptions to this rule. The amount of organic change, as Pictet has remarked,

does

not →OMIT the same →in each successive so-called formation. Yet if we compare any but the most closely related formations, all the species will be found to have undergone some change. When a species has once disappeared from the face of the earth, we have

reason

no reason

to believe that the same identical form

never

ever

reappears. The strongest apparent exception to this latter

rule,

rule

is that of the so-called "colonies" of M. Barrande, which intrude for a period in the midst of an older formation, and then allow the pre-existing fauna to reappear; but

Lyells

Lyell's

explanation, namely, that it is a case of temporary migration from a distinct geographical province, seems

to me

....

satisfactory.

These several facts accord well with

our

theory.

theory,

→which includes no fixed law of development, causing all the inhabitants of

a country

an area

to change abruptly, or simultaneously, or to an equal degree. The process of modification must be

extremely

....

→slow, and will generally affect only a few species at the same time;

The

for the

variability of each species is

quite

....

independent of that of all others. Whether such →variations or individual differences as may arise will be accumulated through natural

selection,

selection

→in a greater or

lesser amount,

less degree,

thus causing a greater or

lesser

less

amount,

amount

→of →permanent modification, will

depends

depend

on many complex

contingencies,—

contingencies—

on the

variability

variations

being of a beneficial nature, on the

power

freedom

intercrossing

intercrossing,

and on

the →OMIT slowly changing physical conditions of the country, →OMIT on the

nature

immigration

of →new colonists, and on the nature of the other inhabitants with which the varying species

comes

come

into competition. Hence it is by no means surprising that one species should retain the same identical form much longer than others; or, if changing,

that it

....

should change →in a less degree. We →find similar relations between the existing inhabitants of distinct countries; for instance,

....

the land-shells and coleopterous insects of Madeira

having

have

come to differ considerably from their nearest allies on the continent of Europe, whereas the marine shells and birds have remained unaltered. We can perhaps understand the apparently quicker rate of change in terrestrial and in more highly organised productions compared with marine and lower productions, by the more complex relations of the higher beings to their organic and inorganic conditions of life, as explained in a former chapter. When many of the inhabitants of

a country

any area

have become modified and improved, we can understand, on the principle of competition, and →from the