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Show 106 MR. W. BATESON ON [Feb. 2, The case of the great variability of the teeth of the large Anthropoids, which is shown not merely in numerical changes, but in frequent abnormalities of position and arrangement, is most striking, both when it is compared with the great rarity of variations in the teeth of the Old World Monkeys and the comparative rarity of great variations even in Man. If the Seals or the Anthropoids had happened to be domesticated animals, I do not doubt that many persons would have seen in this variability a consequence of domestication. When the whole evidence is examined, it will be found that we can make no generalizations of this kind, and that the variability of a form is, so far as can be seen, as much a part of its specific characters as any other feature of its organization. A few curious cases may be given in illustration. Of Canis cancrivorus, a S. American Fox, I know the following specimens only (in the British Museum)-normals (numerically) : one whole skull with lower jaw, one skull without lower jaw, and one lower jaw without a skull, and in one of these right m 3 is much larger than the corresponding left tooth; abnormals: two skulls have m4 on both sides, and a third has a large " odontome" formed as 4 small molars growing from right m3. Of Felis fontanieri, an aberrant Leopard, two skulls only are known (British Museum), and both of these show dental abnormalities, one having supernumerary left m2, and the other having an additional talon to right p3, making it almost a " bigeminous " tooth. In the Seals only three cases of reduplication of the first premolar were seen, and two of these were in Cystophora cristata (Leyden and Cambridge). Evidence of this kind might be multiplied indefinitely. The following cases are chosen as representative examples or "Prerogative Instances" of different classes of phenomena which occur in connexion with increase in number of teeth. It will be understood that the cases are selected as illustrations, and that in order to have a full appreciation of their significance, the whole body of evidence must be taken together, for scarcely any two cases are exactly alike. Division of individual Teeth. Ommatophoca rossii.-Of this form two skulls only are known, namely, those in the British Museum. One of them has the arrangement usually found in Phocidae, viz., five teeth behind the canines, giving the formula:-i. 2~2, c. j ~ , p. -f- m.J^f. By the analogy of other Seals, these five teeth are p. \, m. \. The other specimen is exceedingly remarkable (fig. 1). In it the incisors and the canines are the same as in the first specimen, but the first tooth behind the canine on both sides in the lower jaw and on the right side in the upper jaw has a very peculiar form, having a deep groove passing over the whole length of the tocth on both its outer and inner sides. These grooves extend from the tip of the root along both sides of the crown, and thus imperfectly divide each tooth into an anterior and a posterior half. The cusp of each tooth |
