Origin of Species Variorum

→ have probably been 1866

was, from the reasons lately assigned, probably 1869

was probably 1872

→ these same species 1866

it 1869 1872

→ in the case of 1859 1860 1861 1866 1869

with 1872

→ effected by palæontologists. 1859 1860 1861 1866 1869

done. 1872

→ OMIT 1860 1861 1866 1869 1872

CHAP. IX. GEOLOGICAL RECORD. 1859

→ distinct species from their European representatives, and by other conchologists as only 1866

only 1859 1860 1861 1869 1872

→ only by the future geologist 1859 1860 1861 1866 1869

by the future geologist only by his 1872

measured by years, →have probably been short in comparison with

that

the periods

during which →these same species remained without undergoing any change. We may infer that this has been the case, from there being no inherent tendency in organic beings to become modified or to progress in structure, and from all modifications depending, firstly on long-continued variability, and secondly on changes in the physical conditions of life, or on changes in the habits and structure of competing species, or on the immigration of new forms; and such contingencies will supervene in most cases only after long intervals of time and at a slow rate. These changes, moreover, in the organic and inorganic conditions of life will affect only a limited number of the inhabitants of any one area or country.

It should not be forgotten, that at the present day, with perfect specimens for examination, two forms can seldom be connected by intermediate

varieties

varieties,

and thus proved to be the same species, until many specimens

are

have been

collected from many places; and →in the case of fossil species this

can

could

rarely be →effected by palæontologists. We shall, perhaps, best perceive the improbability of our being enabled to connect species by

numerous,

numerous

fine,

intermediate,

intermediate

fossil links, by asking →OMIT

ourselves

our-selves

whether, for instance, geologists at some future period will be able to

prove,

prove

that our different breeds of cattle, sheep, horses, and dogs

are

have

descended from a single stock or from several aboriginal stocks; or, again, whether certain sea-shells inhabiting the shores of North America, which are ranked by some conchologists as distinct species from their European representatives, and by other conchologists as →distinct species from their European representatives, and by other conchologists as only varieties, are really

varieties

varieties,

or are, as it is called, specifically distinct. This could be effected →only by the future geologist discovering in a fossil state numerous intermediate

gradations;

gra- dations;