rising and enlarging tract of land, than on an area of
subsidence. Nor do I know whether there are more "fine" species on
isolated volcanic islands in process of formation, than on a continent;
but I may remark, that at the Galapagos Archipelago the number of forms,
which according to some naturalists are true species, and according to
others are mere races, is considerable: this particularly applies to the
different species or races of the same genera inhabiting the different
islands of this archipelago. Furthermore it may be added (as bearing on
the great facts discussed in this chapter) that when naturalists confine
their attention to any one country, they have comparatively little
difficulty in determining what forms to call species and what to call
varieties; that is, those which can or cannot be traced or shown to be
probably descendants of some other form: but the difficulty increases,
as species are brought from many stations, countries and islands. It was
this increasing (but I believe in few cases insuperable) difficulty
which seems chiefly to have urged Lamarck to the conclusion that species
are mutable.

CHAPTER VII

ON THE NATURE OF THE AFFINITIES AND CLASSIFICATION OF ORGANIC
BEINGS{425}

{425} Ch. XIII of the _Origin_, Ed. i., Ch. XIV Ed. vi. begins with
a similar statement. In the present Essay the author adds a
note:--"The obviousness of the fact (_i.e._ the natural grouping of
organisms) alone prevents it being remarkable. It is scarcely
explicable by creationist: groups of aquatic, of vegetable feeders
and carnivorous, &c., might resemble each other; but why as it is.
So with plants,--analogical resemblance thus accounted for. Must
not here enter into details." This argument is incorporated with
the text in the _Origin_, Ed. i.

_Gradual appearance and disappearance of groups._

It has been observed from the earliest times that organic beings fall
into groups{426}, and these groups into others of several values, such
as species into genera, and then into sub-families, into families,
orders, &c. The same fact holds with those beings which no longer exist.
Groups of species seem to follow the same laws in their appearance and
extinction{427}, as do the individuals of any one species: we have
reason to believe that, first, a few species appear, that their numbers
increase; and that, when tending to extinction, the numbers of the
species decrease