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Show 18/8] CLASSIFICATION OF THE CERVID.E. 895 Facts (continued). (3) The antlers of the European Procervulus and of some species of the North-American Cosoryx appear to have been persistent. (4) The antlers of Dicroceros and Cosoryx possessed one, or at most two tines. (5) The increase in the complexity of the antlers of extinct species accompanies their chronological sequence in geological time. (6) In a conversation which I have lately had with Prof. Marsh, he informed me that some of the specimens of Cosoryx collected by him in North America were tetradactyle. The lateral metacarpals in these specimens are excessively attenuated in the centre third of their length. In other specimens Prof. Marsh tells m e a natural separation had taken place between the proximal and distal ends of the bones. (7) The condition of the lateral metacarpals separates existing Deer into two great groups, the Plesiometacarpi and Telemetacarpi. Hypothesis (continued). remained unantlered; andspread-from the centre of their geographical area (13), which was probably in the Eastern Palaearctic and Indian regions, they passed westward into Europe, and eastward into North America. (3) Processes then became developed from the frontals, which gradually elongated and in some instances branched. At first these outgrowths from the frontals remained persistently attached; but eventually the great advantage enjoyed by individuals who through necrosis lost, and through an inherited tendency to produce frontal processes renewed their antlers, over individuals who retained antlers broken and rendered useless by frequent combats, caused the natural selection of the former in the struggle for existence. (4, 5) These first deciduous antlers were exceedingly simple ; but as time rolled on the advantage of large and complex antlers as a means of offence and defence established an ever-increasing tendency towards complexity in their form. (6) A diminution in the size of the lateral digits of the early forms of Deer accompanied the increase in the size of their antlers. The centre part of these bones, after attaining an extreme degree of atrophy, at last ceased to ossify. (7, 8) In some species the default in ossification took place nearer the distal than the proximal extremity of the bone. In others the converse obtained. The reduction of the rudiments steadily continued, resulting eventually in the disappearance of the shorter rudiment in both forms. Hence the origin of the plesiome- |
