rect that in
good birds the head and tail touch; the oil-gland is quite aborted. Several
other less distinct breeds might be specified.

In the skeletons of the several breeds, the development of the bones of the
face in length and breadth and curvature differs enormously. The shape, as
well as the breadth and length of the ramus of the lower jaw, varies in a
highly remarkable manner. The number of the caudal and sacral vertebrae
vary; as does the number of the ribs, together with their relative breadth
and the presence of processes. The size and shape of the apertures in the
sternum are highly variable; so is the degree of divergence and relative
size of the two arms of the furcula. The proportional width of the gape of
mouth, the proportional length of the eyelids, of the orifice of the
nostrils, of the tongue (not always in strict correlation with the length
of beak), the size of the crop and of the upper part of the oesophagus; the
development and abortion of the oil-gland; the number of the primary wing
and caudal feathers; the relative length of wing and tail to each other and
to the body; the relative length of leg and of the feet; the number of
scutellae on the toes, the development of skin between the toes, are all
points of structure which are variable. The period at which the perfect
plumage is acquired varies, as does the state of the down with which the
nestling birds are clothed when hatched. The shape and size of the eggs
vary. The manner of flight differs remarkably; as does in some breeds the
voice and disposition. Lastly, in certain breeds, the males and females
have come to differ to a slight degree from each other.

Altogether at least a score of pigeons might be chosen, which if shown to
an ornithologist, and he were told that they were wild birds, would
certainly, I think, be ranked by him as well-defined species. Moreover, I
do not believe that any ornithologist would place the {23} English carrier,
the short-faced tumbler, the runt, the barb, pouter, and fantail in the
same genus; more especially as in each of these breeds several
truly-inherited sub-breeds, or species as he might have called them, could
be shown him.

Great as the differences are between the breeds of pigeons, I am fully
convinced that the common opinion of naturalists is correct, namely, that
all have descended from the rock-pigeon (Columba livia), including under
this term several geographical races or sub-species, which diff