OCR Text |
Show 1892.] NUMERICAL VARIATION IN TEETH. 105 panzee, and Gorilla-141 normal skulls were seen, and 11 cases of supernumerary teeth, or nearly 8 per cent, (in addition to 7 recorded cases known to me). On the other hand, no case was seen in 51 skulls of Hylobates, which were all normal. And of Old World Monkeys other than these, I found only two cases in 423 skulls, or less than -5 per cent. In the species of Cebidae and in Ateles supernumerary teeth are common, five cases being found in 131 skulls, or nearly 4 per cent, (in addition to 4 recorded cases); while in 92 skulls of other N e w World Monkeys there was not one case. PHOCIDJE.-139 normals, 11 cases of supernumerary teeth, or 7'5 per cent. OTARIID^E.-121 normals, 5 cases of supernumerary teeth, or 4 per cent. CANiDiE.-Of wild Canidae, 289 normals were seen, and 9 cases of supernumerary teeth, or 3 per cent, (in addition to numerous recorded cases). Of Domestic Dogs, including Pariahs, &c, 200 skulls were normal and 16 had supernumerary teeth, or 8 per cent. (besides many recorded cases). FELiDiE.-Of wild Felidae, 278 normals and 6 cases of supernumerary teeth, or more than 2 per cent. Of Domestic Cats, 35 normal and 3 cases of supernumerary teeth, or 9 per cent. ViVERRiD^E.-94 normals (not regarding variations affecting the first premolar only) and 4 cases of supernumerary teeth. Owing to the great variability of the dentition of some groups of Marsupials and the difficulty of deciding on the normal formula, it would not be profitable to give summary statistics which should be satisfactory. It will be seen that, so far as the statistics go, supernumerary teeth were more common in domestic Dogs than in wild Canidae, and though the number of Cats seen was small, the same is true in their case also as compared with wild Felidae. But though it is received by many almost as an axiom that domestic animals are, as such, more variable than wild ones, and though the figures somewhat support this view, it is necessary to point out that such a deduction should be made with great caution. For while it is true that the domestic Dog is more variable in its dentition than wild Dogs, it is not true that it is much more variable than many other wild animals, as, for example, the Anthropoid Apes, some of the Phocidae, several genera of Marsupials, and others. The doctrine that domestication induces or causes Variation is one which will not, I think, be maintained in the light of fuller evidence as to the Variation of wild animals. It has been suggested by the circumstance that so many of our domesticated animals are variable forms, and that so little heed has been paid to the variation of wild forms. To obtain any just view of the matter, the case of variable domestic species should be compared with a species which is variable though wild. |