982 MR. H. I. POCOCK ON THE [June 14, 



sliallowei- <j;lan(lul:ir depression such as is seen in A. axis and 

 A, porcinus; and also on the other side how by the gradual 

 shallowing of the depression in the feet of these last-named species 

 the condition of things found in the feet of the Ked Deer (C 

 elaphns) and its allies has been reached, 



I do not by any means wisli to suggest that the species named 

 stand in the exact line of descent to one another; but I do think 

 it probable that their pedal glands represent approximately the 

 stages through which the various types of pedal glands met with 

 in the Cervida? have passed in their evolution. 



Similar stages in the gradual obliteration of the interdigital space 

 accompanied by the evolution of differentiated pedal glands and 

 their linal suppression may be traced in the Bovida?. In Madoqua, 

 liaphicerus, and Cephalopkns, for instance, the digits of the pastern 

 are held together by a long and clcjse fold of integument constituting 

 a web which extends down or nearly down to the heels; the anterior 

 skin of this fold forms the posterior wall of the glandular inter- 

 digitiil cleft, as in Cervidus and Dama. This cleft is at first open 

 below betweeii the hoofs and remains so in Madoqua and Cej)ha- 

 lophus. But in both these genera, as well as in Baphicerus and 

 Dorcotragus, the orifice of the cleft is shortened to a greater or less 

 extent, according to the species, by the downward extension 

 towards the hoofs of the folded integument of the anterior 

 surface of the pastern, forming a longer or shorter anterior wall 

 to the enclosed glandular space. Another simple modification is 

 seen in the Gazelles, in which, while the orifice of the cleft retains 

 almost unchanged in its original length, its inferior portion is 

 closed and shut off from the interungual space by the anterior 

 extension of the posterior web from the heels to the front of the 

 lioof. I'ractically the same structural change has taken place in 

 the Oribi {Oarehia)i\x\'\ in the Hartebeests {Bubalis, Damalisctis), 

 except that in JJabalis the anterior web overlaps the cavity to a 

 consideral)le extent above and in front. 



The adult White-tailed Gnu [Connochcetes gnu) exhibits a 

 further stage in the evolution of the gland seen in the Hartebeest, 

 the orifice of the cleft being still more shortened and the posterior 

 integumental web not so closely folded. A further stage in the 

 closing up of the orifice of the cleft is exemplified by the feet of 

 Oryxheisa; and this is followed by the reduction of the orifice 

 to a small circular aperture as in Hippotragus, Pelea, JYcemorhedns, 

 and Ovis; the final sfcige, sometimes certainly and always probably 

 of sporadic occurrence within the limits of a species, being the 

 retention of mei-ely the orifice and part of the duct of the gland 

 as in JRedunca, Capra, J/emitragti.s, and Pseudois. 



If this be the correct view of the evolution of the feet, there must 

 l)e some reason or reasons for the disappeai-ance of interdigital 

 clefts. It seems certain that large interdigital clefts must be a 

 source of weakness to the feet. Although a foot with its two 

 component digits united by a close fold of integument extending 

 from the heels up the back of the piustern is more suitable, on 



