OCR Text |
Show 890 SIR v. BROOKE ON THE [Nov. 19, The question as to whether these minor groups should be regarded as genera or subgenera, or merely marked as nameless sections, appears to m e to be of wholly secondary importance. Actuated by this belief, I have retained the names originally given to these subgroups whenever the grouping has appeared to m e to be natural, and have spoken of them as subgenera. The characters upon which the subgenera are based are derived principally from the form of the antlers, the skull, the rhinarium1, external coloration, position and degree of development of the cutaneous glands, and general external form. As is the case with the family characters, it is seldom that any one subgeneric peculiarity can be taken singly as exclusively characteristic of a certain subgenus; but the existence in different fixed combinations of these characters in the several subgenera is an empirical certainty. For example, the form of rhinarium peculiar to Busa (vide infra) is shared by other groups, but never in combination with the form of antler and immense lacrymal pit typical of that subgenus; and no species of Busa is without this combination. Again, the form of the rhinarium in the subgenus Cervus differs from that of Rusa, but resembles that of Darna &c. ; but in Cervus this rhinarium is always associated with the antlers typical of that subgenus, and an anal disk of paler colour than the adjacent parts surrounding the tail; whilst in Darna it is combined with the palmated form of antler and tuft of long hair surrounding the prepuce. It is needless here to give further examples of this law : it will be found fully illustrated in the diagnoses of the subgenera (imperfect as these doubtless are) given in the synopsis. The objection that antlers are absent in the females of all existing species with the exception of Bangifer, whilst in Hydropotes they are wanting in both sexes, has been frequently urged against the value of characters based on these appendages. The stability of this objection strikes m e as very questionable. There can be no doubt that it would be highly convenient if such prominent and easily observed features as those afforded by the antlers were universally attainable; and the lack of their invariable occurrence is doubtless a source of some slight confusion to the systematist. But surely the value of a character as a test of genetic affinity cannot be judged upon utilitarian principles ; and if, as I think, I can show reason for believing the form of the antlers is one of the clearest proofs of the blood-relationship of the species contained in the various subgenera, characters derived therefrom must be regarded as the most trustwothy for taxonomic purposes. In order to account for the phenomena presented by the antlers in the males of the existing Deer, four factors are necessary :- (1) The gradual evolution of the antlers from very simple to complex forms; (2) Their constant tendency to vary ; (3) Variation extending far enough to induce the partial atrophy of one part of the antler 1 I follow Illiger and Sundevall in the adoption of this term for tbe naked moist skin between the nostrils. It is decidedly preferable to muffle, which is French, or muzzle, which signifies something quite different in every-day speech. |