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Show 260 PROF. KARL BARDELEBEN ON [May 7, occasions frustrated. In the meantime, many observations agreeing with m y own have been recorded by other authors ; and there has been a strong attack made upon my views by Prof. Gegenbaur (Morphol. Jahrbuch, vol. xiv. p. 394, 1888). This attack, emanating from one of the most celebrated comparative anatomists of the day, impelled me to renew my investigations on the subject and, for this purpose, to study the collections preserved in the British Museum, where I have found both a very large amount of material and have met with the greatest kindness in helping me to use it. Of those to whom I am particularly indebted, I may mention Prof. Flower, Dr. Giintber, Dr. Woodward, Mr. Boulenger, Mr. Lydekker, and especially Mr. Oldfield Thomas, who allowed me to work in his room, and who gave m e much assistance in m y examination of the Museum specimens. These recent observations have fully corroborated my previous conclusions on the subject. Although it is not possible for me just now to communicate ail tbe results I have obtained in London, I may nevertheless give a short account of some of the more interesting facts which I have established. In some Mammals (for example, in Pedetes capensis) the praepollex consists of two bones (Plate X X X . fig. 2), of which, in a specimen in the British Museum, the proximal (Pp.p.)is 13 millim. long, and the distal (Pp.d.) 7 millim. And, above all, this rudiment of a digit bears, in this animal, a genuine nail1 ; whereas many true digits, such as the halluxes of Marsupials, are without nails. The praepollex of Pedetes is very large, and the nail is a true one, singularly like that of the human thumb and similarly longitudinally striate (Plate X X X . fig. 1). In Bathyergus mantimus (Plate X X X . fig. 3) the praepollex and the postminimus are both very well developed. The latter consists of two bones, of which the proximal (pi.p.) is the true pisiform and measures 5 millim. in length, while the distal (pi.d.) is 7*5 millim. in length. W e must therefore in the future distinguish a proximal from a distal " pisiform ;" and I regard the former as, in all probability, the carpal, and the latter as the metacarpal segment of the postminimus. If, with the carpus or tarsus of an animal with five digits, there articulate one or two supernumerary bones having the form and relationships of those ordinarily representing a reduced pollex or hallux, we have good reason for regarding the same as rudiments of a digit. It is most difficult, however, to say wherein a digit consists. How many bones must it contain ? Is the mammalian thumb invariably a complete digit, or is it only a rudiment? If it is a digit, the praepollex and praehallux are digits too, at least in the cases of Pedetes, Talpa, and many others. Everybody who has 1 Mr. Oldfield Thomas, to whom I had shown the two bones in the prs-pollex, examined for m e the skins of this animal which are preserved in the collection, and found the nail in question. Prof. Howes has since informed m e that a similar, but less specialized, cornification overlies the immeuse prce-hallux of Ccrcolabcs (C. novee-hispaniee). |
