is M. Gay examined twenty-nine embryos, and of these sixteen were
vigorously 'pleurorhizees,' nine had characters intermediate between
pleuro-and notor-hizees, and four were pure notor-hizees."

"M. Raspail asserts (_Ann. des Scien. Nat._, ser. i. tom. v. p. 440)
that a grass (Nostus Borbonicus) is so eminently variable in its floral
organisation, that the varieties might serve to make a family with
sufficiently numerous genera and tribes--a remark which shows that
important organs must be here variable."

_Species which vary little._

The preceding statements, as to the great amount of variation occurring
in animals and plants, do not prove that all species vary to the same
extent, or even vary at all, but, merely, that a considerable number of
species in every class, order, and family do so vary. It will have been
observed that the examples of great variability have all been taken from
common species, or species which have a wide range and are abundant in
individuals. Now Mr. Darwin concludes, from an elaborate examination of
the floras and faunas of several distinct regions, that common, wide
ranging species, as a rule, vary most, while those that are confined to
special districts and are therefore comparatively limited in number of
individuals vary least. By a similar comparison it is shown that species
of large genera vary more than species of small genera. These facts
explain, to some extent, why the opinion has been so prevalent that
variation is very limited in amount and exceptional in character. For
naturalists of the old school, and all mere collectors, were interested
in species in proportion to their rarity, and would often have in their
collections a larger number of specimens of a rare species than of a
species that was very common. Now as these rare species do really vary
much less than the common species, and in many cases hardly vary at all,
it was very natural that a belief in the fixity of species should
prevail. It is not, however, as we shall see presently, the rare, but
the common and widespread species which become the parents of new forms,
and thus the non-variability of any number of rare or local species
offers no difficulty whatever in the way of the theory of evolution.

_Concluding Remarks._

We have now shown in some detail, at the risk of being tedious, that
individual variability is a general character of all common and
widespread species of animals or plants; and, further, that