SCIIIN. YOSCIIIDA 185 
among animals so that when they walk on soft or marshy ground they may 
not sink too deeply into the yielding earth, and when the animal is accus- 
tomed to walk on steep hilly ground the after claw is needed as a support. 
These less rudimented after claws of the ox and deer are of similar develop- 
ment on fore and hind feet, but among the Ungulata, which have a quite 
rudimented after claw, we find a difference in the size on the fore and hind 
limbs. In particular, the after claw on the forefoot of the Madoquo Phillipsi 
is very small and that on the hind foot very large. 
I have obtained the following result, that the more rudimented and use- 
less the after claws the nearer they are together. For example, the fully 
rudimented after claws of the Dorcotragus Megarotis (PI. VIII. Fig. 2), es- 
pecially on the forefoot are c]uite close together and appear as one ; the claw 
wall of its after claw has been thrown off and it has the appearance of a pad. 
In particular, when the histological structure of such a fully rudimented 
after claw is seen, the Hapillae are simpler than in the Ergot and Callosity of 
Equidae, and the hornined cell layer is thicker, that is the Stratum Corneum 
is not degenerated, than in the Ergot and Callosity. 
That the Callosity and Ergot which have a more developed histological 
structure than the after claw of the Dorcotragus, should be rudimentary pads 
is not to be considered, because, as I have written above, the pad which is 
still functional is less developed than the Callosity and Ergot. I must here 
describe what I mean by the development of a hornified mass, which I have 
sometimes mentioned. This is the degree of development of the Papillae in 
the hornified tissue and of the horny layer. Because the Papillae always con- 
tain fine blood v^essels which carry nourishment to the layers above, when the 
Papillae are developed the layers above will be equally so ; such a fact may 
be seen in every hornified mass found on mammals, for example, in the fully 
developed hoof of the horse quite complicated Papillae may be seen with 
secondary Papillae. From such complicated Papillae to those of simple, 
nearly flat form which are found in the tissue of the very little developed 
hornified skin, the degree of development of the hornified mass is divided 
