1902.] CARPAL VIBRI33JE IX MAMMALS. 133 



summaiy of the facts at my disposal, the vibrissEe wei'e only to be 

 found in the fore limbs. In some cases I admit I did not ex- 

 amine with great care the tarsus as well as the cai-pus. But after 

 finding that in one species (illustrated in text-figs. 18, 19, pp. 130, 

 131) both fore and hind limbs shoAved a precisely similar tuft of 

 vibrisspe, I naturally examined other animals that came my way. 

 In Petaurus sciureits, in fact, this tuft of sensory hairs is present 

 on both pairs of lim.bs, occupying a corresponding position in each. 

 There was no difference that I could detect in the arrangement 

 or structure of the vibrissas in the two limbs. The case appears 

 to me to be simply another instance of structures appearing in 

 one pair of lim^bs being repeated in the other, — just as the horny 

 spine-like outgrowths of the wrist of Hapalemicr griseus are found 

 on the ankle of Gcdago garneMi \ 



The accompanying illustration (text-fig. 20, p. 132) shows the tuft 

 of carpal vibriss?e in a Ooati with the skm-flap removed and the 

 muscles partly dissected. In this animal the tuft consists of six 

 long black hairs, the implantation of which on the skin is shown 

 in the drawing. The roots of these vibrissa; are provided with a 

 nervous supply in the shape of a sti'ong branch leaving the main 

 nerve of the arm just opposite to the tuft, and ending after a shoit 

 course without any sensible diminution of thickness and without 

 any branching visible to the naked eye. This marked nervous 

 supply to the cai'pal sense-organ is not, however, invariably found. 

 The most abei-i-ant condition of this cai'pal organ in all the animals 

 which I have examined exists in Hyrax. In this Ungulate, the 

 only Ungulate in which I have been able to detect the organ at 

 all, I could only find it on one of the two fore limbs ; and on that 

 limb, the right, it was represented by only two long hairs, one 

 being situated in the normal position which the tuft occupies in 

 other mammals, and the other placed some way behind this. On 

 carefully dissecting away the skin the i-oots of the haii-s wei'e ex- 

 posed, and their gi'eat size enabled it to be seen that thei'e were 

 two of them, though only one haii- was visible extei-nally. In the 

 case of the posterior tuft I could find but one hair-bulb. This 

 state of affairs is shown in the drawing exhibited herewith (text- 

 fig. 21, p. 134). The most careful examination fa-'led to show 

 any nerve-branch supplying the roots of the vibrissae. I have no 

 doubt that minute microscopic threads exist ; but there is nothing 

 that can be detected with the naked eye to be seen ; and I think 

 that it could hardly have been overlooked. Now it appears to 

 me that we have in this animal a case of commencing retro- 

 gression of the organ in question. It can hardly be denied that 

 Hyrax stands at least nearer to the base of the Ungulate seiies 

 than do the Pei'issodactyla or the Artiodactyla. Thei'efore it is 

 not surprising to find in Hyrax traces of a structui-e that has 

 entirely disappeared in the more specialized forms ; and in effect 



' See Beddard, P. Z. S. 1884, p. 393, and ibid. 1901, vol. i. p. 272. 



