22 
DOMESTIC PIGEONS. 
Chap. I. 
carried so erect 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 develop¬ 
ment 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 vertebrsD vary; as does the num¬ 
ber 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 correla¬ 
tion 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 scutelte 
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 
