crown is deeper, the posterior groove is continued lower down upon the fang, and the ridge between the two grooves is more prominent than in the Troglodytes niger. Both premolars,

Dentition of upper jaw, male Troglodytes Gorida, nat. size. ct'.

fig. 255, p 3, and p 4, are bicuspid; the outer cusp of the first, and the inner cusp of the second being the largest, and the first premolar, p 3, consequently appearing the largest on an external view. The difference is well marked in the female, fig. 254, p 3. The anterior external angle of the first premolar is not produced as in the Orang, which in this respect makes a marked approach to the lower Quadrumana. In Man, where the outer curve of the premolar part of the dental series is greater than the inner

one, the outer cusps of both premolars are the largest; the alternating superiority of size in the Gorilla accords with the straight line which the canine and premolars form with the true molars. In fig. 255, m 1, m 2, m 3, are quadricuspid, relatively larger in comparison with the bicuspids than in the Orang. In the first and second molars of both species of Troglodytes a low ridge connects the antero-internal with the postero-external cusp, crossing the crown obliquely, as in Man. There is a feeble indication of the same ridge in the unworn molars of the Orang; but the four principal cusps are much less distinct, and the whole grinding surface is flatter and more wrinkled. In Troglodytes niger the last molar is the smallest, owing to the inferior development of the two hinder cusps, and the oblique connecting ridge is feebly marked. In Troglodytes Gorilla this ridge is as well developed as in the other molars, but is more transverse in position; and the crown of m 3 is equal in size to that of m1 or m2, having the posterior outer cusp, and particularly the posterior inner cusp, more distinctly developed than in Troglodytes niger. The repetition of the strong sigmoid curves which the unworn prominences of the first and second true molars present in Man, is a very significant indication of the near affinity of the Gorilla as compared with the approach made by the Orangs or any of the inferior Quadrumana, in which the four cusps of the true molars rise distinct and independently of each other. A low ridge girts the base of the antero-internal cusp of each of the upper true molars in the male Chimpanzees; it is less marked in the female. The premolars as well as molars are severally implanted by one internal and two external fangs. In no variety of the human species are the premolars normally implanted by three fangs; at most the root is bifid, and the outer and inner divisions of the root are commonly connate. It is only in the black varieties, and more particularly that race inhabiting Australia, that I have found the wisdom-tooth,' fig. 257, m 3, with three fangs as a general rule; and the two outer ones are more or less confluent. The lower canine of the male (figs 253, 256, c), shows the same relative superiority of size as the upper one, compared with that in the female, in both species of Troglodytes. The canine almost touches the incisor, but is separated by a diastema one line and a half broad from the first premolar. This tooth p3, is larger externally than the second premolar, and is three times the size of the human first premolar, fig. 257, p3; it has a subtriedral crown, with the anterior and outer angle produced forward, slightly indicating the peculiar features of the same tooth in the

Baboons, but in a less degree than in the Orang. The summit of the crown of p 3 terminates in two sharp triedral cusps-the outer one rising highest and the second cusp being feebly indicated on the ridge extending from the inner side of the first; the crown has also a thick ridge at the inner and posterior part of its base. The second premolar, p 4, has a subquadrate crown, with the two cusps developed from its anterior half, and a third smaller one from the inner angle of the posterior ridge. Each lower premolar is implanted by two antero-posteriorly compressed divergent fangs, one in front of the other, the anterior fang being the largest.

The three true molars are nearly equal in size in the Troglodytes Gorilla, the last being a little larger than the first: in the Troglodytes niger, fig. 256, the first, m 1, is a little larger than the last, m 3, which is the only molar in the smaller Chimpanzee as large as the corresponding tooth in the black varieties of the human subject, in most of which, especially the Australians, fig. 257, the true molars attain larger dimensions than in the yellow or white races. The four principal cusps, especially the two inner

Teeth of right side, lower jaw, of adult male Chimpanzee, (Troglodytes niger), nat. size.

ones of the first molar of both species of Troglodytes, are more pointed and prolonged than in Man; a fifth small cusp is developed behind the outer pair, as in the Orangs and the Gibbons, but is less than that in Man. The same additional cusp is present in the second molar, which is seldom seen in Man. The crucial groove on the grinding surface is much less distinct than in Man, not being continued across the ridge connecting the anterior pair of cusps in the Chimpanzee. The crown of the third molar is longer antero-posteriorly from the greater development of the fifth posterior cusp, which, however, is rudimental in comparison with that in the Semnopitheques and Macaques. All

the three true molars are supported by two distinct and welldeveloped antero-posteriorly compressed divergent fangs; in the white and yellow races of the human subject these fangs are usually connate in m 3, and sometimes also in m 2. The molar series in both species of Troglodytes forms a straight line, with a slight tendency, in the upper jaw, to bend in the opposite direction to the well-marked curve which the same series describes in the human subject.

This difference of arrangement, with the more complex implantation of the premolars, the proportionally larger size of the incisors as compared with the molars; the still greater relative magnitude of the canines; and, above all, the sexual distinction in that respect illustrated by figs. 253 and 254, stamp the Gorillas and Chimpanzees, fig. 256, most decisively with not merely specific but generic distinctive characters as compared with Man. For the teeth are fashioned in their shape and proportions in the dark recesses of their closed formative alveoli, and do not come into the sphere of operation of external modifying causes until the full size of the crowns has been acquired. The formidable natural weapons of the males of both species of Troglodytes, form the compensation for the want of that psychical capacity to forge or fashion destructive instruments which has been reserved, as his exclusive prerogative, for Man. Both Chimpanzees and Orangs differ from the human subject in the order of the development of the permanent series of teeth; the second molar, m 2, comes into place before either of the premolars has cut the gum, and the last molar, m 3, is acquired before the canine. We may well suppose that the larger grinders are earlier required by the frugivorous Chimpanzees and Orangs than by the higher organised omnivorous and longer nursed Bimanal, with more numerous and varied resources, and probably one main condition of the earlier development of the canines and premolars in Man may be their smaller relative size.

F. Bimana. Having reached, in the Gorilla, the highest step in the series of the brute creation, our succeeding survey of the dental system, cleared and expanded by retrospective comparison, becomes fraught with peculiar interest, since every difference so detected establishes the true and essential characteristics of that part of man's frame.

The human teeth are the same in number and in kind as those of the catarhine Quadrumana. The bimanal dental formula is therefore

that is to say, there are on each side of the jaw, both above and below, two incisors, one canine, two premolars, and three true molars.

They are more equal in size than in the Quadrumana. No tooth surpasses another in the depth of its crown; and the entire series, which describes in both jaws a regular parabolic curve, is uninterrupted by any vacant space (vol. ii., fig. 182). The most marked distinction between the bimanal dentition and that of the highest Quadrumanals, is the absence of the interval between the upper lateral incisor and the canine, and the comparatively small size of the latter tooth; but its true character is indicated by the conical form of the crown, which terminates in an obtuse point, is convex outward, and flat or sub-concave within, at the base of which surface there is a feeble prominence. The conical form is best expressed in the Melanian races, especially the Australian, fig. 257, c. The canine is more deeply implanted, and by a stronger fang than the incisors; but the contrast with the Chimpanzee is sufficiently manifest, as is shown in fig. 256, c. There is no sexual

superiority of size either of the canine or any other single tooth in the human subject.'

1 In honest argument as to Man's place in Nature, his zoological characters are to be compared with those of the brute that comes nearest to him; the differences so established should be contrasted with those between such brute, the gorilla, e. g., and the next step in the scale, the chimpanzee, e. g.; and so on, step by step, through the order which Zoology forms of the series of species so gradually differentiated. No doubt a gorilla differs more in its dentition from a lemur, and still more from a mole or a mouse, than it differs from Man. Take another character-the hinder or lower limbs, e.g.; contrast the Negro in this respect with the gorilla, and, next, that ape with any other quadrumanal. Much as the aye-aye differs as a whole, from the gorilla, it does resemble it more in such quadrumanal structure than the gorilla resembles Man. Between the two extremes of the four-handed series there is greater organic conformity in the main ordinal character than exists between the highest ape and the lowest man. Or take the cerebral test. Man's place in the Natural System is to be judged, not by the degree of difference between the brain of an ape and that of a mammal one hundred links removed; but by the degree of difference between the human brain and that of the brute which comes nearest to him, as contrasted with the degree of difference between the brains of the gorilla and chimpanzee, or between those of any other two conterminous species constituting links in the quadrumanous chain. The difference between figs. 147 and 148-9 may be greater than between 149