314 MR. W. P. PYCRAFT ON THE BIRD’S WING 
structure. He will assume for this limb a primitive pentadactyle 
form with numerous separate carpal bones ; this primitive five- 
fingered or pentadactyle form being the common type to which 
every fore- and hind-limb, above that of the fishes, can be reduced. 
By way of testing such a conclusion, the carpus, or wrist, and 
hand of the nestling bird will be first examined. Such an 
examination will show, as will be seen in Fig. 1, that the 
metacarpals, only imperfectly distinguishable in the adult, are 
now seen distinctly as three separate elements (Me 1, 2, 3), whilst 
in addition to the two free carpals of the adult (r 7 u 77 ) he will 
find a third distinct semi-lunar mass capping the bones of the 
metacarpals (D.c) and representing, therefore, a some-time separate 
row of distinct carpal bones. This region of the wing, at this 
stage, it is significant to note, exactly corresponds with the perma- 
nent condition of the same region in the ancient Archceopteryx. 
Turning now to the embryo, if he be fortunate, he will find, in 
addition to the two proximal carpals of the adult, — the radiale 
and the ulnare — a third element, the intermedium ; whilst the 
fused distal mass of the nestling will now be seen to consist 
of several distinct elements. Furthermore, traces will be found 
of at least one of the postulated primitive five digits in addition 
to the three which permanently remain. 
Remembering that all the modifications which this limb has 
undergone have been to further the ends of flight, he will turn 
next to such other cases as may be found in which this limb has 
become transformed for similar ends. The Bat and the extinct 
Pterodactyle will be found the only vertebrate parallels, and it 
is with these that the wing of the bird will now be compared. 
A comparison of the wings of these three forms would at once 
reveal a very striking difference between the bird’s wing and that 
of the Bat and the extinct flying Lizard. In the two latter 
(Fig. 2, A, B,) we should find that the wing was formed by 
a sheet of membrane, extending from the body outwards to the 
tip of the fore-limb, and supported by one or more digits ; whilst, 
in the bird, the membrane is more or less completely replaced 
by a system of separate, elongated, overlapping blades, differing in 
nowise, save in size, from the general and remarkable body-clothing 
which we know as feathers. These overlapping blades we know as 
the remiges or quill feathers. 
