Origin of Species Variorum

→ in any one region for the immigration of 1860 1861 1866 1869 1872

for the coming in of quite 1859

→ from other regions, 1860 1861 1866 1869 1872

by immigration, 1859

→ mastodons 1859 1860 1861 1866 1869

the species of mastodons 1872

→ series, first 1859 1860 1861 1866 1869

series,— in the first place 1872

→ then 1859 1860 1861 1866 1869

in the second place 1872

any

great

one great

period in the earth's history will be

inter- mediate

intermediate

in general character between that which preceded and that which succeeded it.

Thus,

Thus

the species which lived at the sixth great stage of descent in the diagram are the modified offspring of those which lived at the fifth stage, and are the parents of those which became still more modified at the seventh stage; hence they could hardly fail to be nearly intermediate in character between the forms of life above and below. We must, however, allow for the entire extinction of some preceding forms, and →in any one region for the immigration of new forms →from other regions, and for a large amount of

modification

modification,

during the long and blank intervals between the successive formations. Subject to these allowances, the fauna of each geological period undoubtedly is intermediate in character, between the preceding and succeeding faunas. I need give only one instance, namely, the manner in which the fossils of the Devonian system, when this system was first discovered, were at once recognised by palæontologists as intermediate in character between those of the overlying carboniferous, and underlying Silurian

systems.

system.

But each fauna is not necessarily exactly intermediate, as unequal intervals of time have elapsed between consecutive formations.

It is no real objection to the truth of the

statement,

statement

that the fauna of each period as a whole is nearly intermediate in character between the preceding and succeeding faunas, that certain genera offer exceptions to the rule. For instance, →mastodons and elephants, when arranged by Dr. Falconer in two →series, first according to their mutual

affinities,

affinities

and →then according to their periods of

existence,—

existence,

do not accord in arrangement. The species extreme in character are not the

oldest,

oldest

or the most recent; nor are those which are