NINTECANNUAL, REPORT: 229 
thus homologous with that in Archaeopteryx. In an Ostrich, 
which I observed closely, and which was almost denuded of 
plumage, I again and again saw a curious and unexpected func- 
tioning of the large second claw. This bird would frequently 
flex the wing at the wrist and elbow, to an extent impossible in 
an ordinary bird of flight, and vigorously scratch its side, and 
even its neck. Ordinarily an Ostrich uses its toe in performing 
the latter action. It was most interesting to see such an unavian, 
quadrupedal act being performed by a bird. 
All the toes of struthious birds are provided with claws—the 
four toes in the Apteryx, three in the Emeu and two in the 
Ostrich. Although almost every text-book of zoology assures 
us that the smaller toe of the latter bird is clawless, yet a claw 
is often present, reduced, however, to about the size of the claw 
on the foot of a common fowl. The short, thick, hoof-like char- 
acter of the claw on the great middle toe of Striuthio is an inter- 
esting parallelism to the hoof of the perissodactyl mammals. 
An adaptation for defence is found in the claw of the inner 
toe of the Cassowary. The other claws are of normal size, but 
this one is very stout, sharp, and about four inches in length, a 
weapon with which the bird can do terrible execution upon an 
enemy at close quarters. 
Little of adaptative interest attaches to the scalation of the leg. 
Although the entire hind limb of the Ostrich is bare of feathers, 
yet this can hardly be explained as due to the increase of function 
of that organ; for in one species of Rhea (/thea darwini), the 
feathering is continued for some distance down, even on the tarso- 
metatarsus. The pink coloring of the bare skin and leg scales 
of some male Ostriches, differing in the different species, seems 
to partake of the nature of a secondary sexual character. 
Il. GENERAL FORM. 
A terrestrial life has had two diverse effects upon the eyes of 
the ratite birds, throwing these organs into two very unequal 
classes ; first, the eyes of the Apteryx, and second, those of other 
members of the Subclass, of which the Ostrich may stand as an 
example. Nocturnal habits, and a diet of earth-worms, as ex- 
plained in Part I., have, in the Apteryx, resulted in the develop- 
ment of the olfactory and tactile senses at the expense of the optic 
power. In the Ostrich, on the contrary, the need for powerful 
vision in detecting enemies upon the open desert, while they are 
yet at a distance, has brought about a remarkably strong develop- 
