The Descent of Man

each breed, without any intention on his part to
modify the characters of the breed. But until I
read an able article in the 'North British Review'
(March 1867, p. 289, et seq.), which has
been of more use to me than any other Review,
I did not see how great the chances were
against the preservation of variations, whether
slight or strongly pronounced, occurring only
in single individuals.) Nevertheless, it may be
worth while to give the few cases which I have
been able to collect, relating chiefly to colour,—
simple albinism and melanism being excluded.
Mr. Gould is well known to admit the existence
of few varieties, for he esteems very slight differences
as specific; yet he states (36. 'Introduction
to the Trochlidae,' p. 102.) that near Bogota
certain humming-birds belonging to the genus
Cynanthus are divided into two or three races
or varieties, which differ from each other in the
colouring of the tail—"some having the whole
of the feathers blue, while others have the eight
central ones tipped with beautiful green." It