difficulty in ascertaining what deserve to
be called species amongst foxes and wolves, and in some birds, for
instance in the case of the white barn-owl. When specimens are brought
from different parts of the world, how often do naturalists dispute this
same question, as I found with respect to the birds brought from the
Galapagos islands. Yarrell has remarked that the individuals of the same
undoubted species of birds, from Europe and N. America, usually present
slight, indefinable though perceptible differences. The recognition
indeed of one animal by another of its kind seems to imply some
difference. The disposition of wild animals undoubtedly differs. The
variation, such as it is, chiefly affects the same parts in wild
organisms as in domestic breeds; for instance, the size, colour, and the
external and less important parts. In many species the variability of
certain organs or qualities is even stated as one of the specific
characters: thus, in plants, colour, size, hairiness, the number of the
stamens and pistils, and even their presence, the form of the leaves;
the size and form of the mandibles of the males of some insects; the
length and curvature of the beak in some birds (as in Opetiorynchus) are
variable characters in some species and quite fixed in others. I do not
perceive that any just distinction can be drawn between this recognised
variability of certain parts in many species and the more general
variability of the whole frame in domestic races.

{218} In Chapter II of the first edition of the _Origin_ Darwin
insists rather on the presence of variability in a state of nature;
see, for instance, p. 45, Ed. vi. p. 53, "I am convinced that the
most experienced naturalist would be surprised at the number of the
cases of variability ... which he could collect on good authority,
as I have collected, during a course of years."

{219} See _Origin_, Ed. i. p. 44, vi. p. 52.

{220} <Note in the original.> Here discuss _what is a species_,
sterility can most rarely be told when crossed.--Descent from common
stock.

{221} <Note in the original.> Give only rule: chain of intermediate
forms, and _analogy_; this important. Every Naturalist at first when
he gets hold of new variable type is _quite puzzled_ to know what to
think species and what variations.

{222} The author had not at this time the knowledge of the meaning
of dimorphi