feathers down the breast; and it has the habit of continually
expanding slightly the upper part of the oesophagus. The Jacobin has
the feathers so much reversed along the back of the neck that they
form a hood, and it has, proportionally to its size, much elongated
wing and tail feathers. The trumpeter and laugher, as their names
express, utter a very different coo from the other breeds. The fantail
has thirty or even forty tail-feathers, instead of twelve or fourteen,
the normal number in all members of the great pigeon family; and these
feathers are kept expanded, and are carried so erect that in good
birds the head and tail touch; the oil-gland is quite aborted. Several
other less distinct breeds might have been 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