746 
Primates (Fig. 3), by a slow upward growth from the cingulum, 
opposite the protocone. In its early stages the hypocone, hy, always 
resembles the early stages of the hypoconid and conclusive proof of 
tis talon-like character is seen among the Condylarthra (Haploconus) 
in which it appears as a wide separate heel. So far therefore, from 
the truth of FLEIscHMANN’s supposition that the upper molars have 
one more element (the ‘“‘entomere”) than the lower, exactly the reverse 
is the case, for the lower molars early acquire much the greatest 
extension of the talon, while retaining all the elements of the trigon. 
A beautiful illustration of the fundamental pattern of trigon and 
talon in the upper human molars is shown in Röse’s figure 6 of the 
molar of a six months child. The protocone makes the apex and is 
connected by two spurs with the two external cusps, the space be- 
tween which is comparatively open as in the primitive forms. 
Thus the homology of the antero-internal cusp of the upper molar 
with the protocone is well supported by palaeontology and by dental 
mechanics but how shall we meet the embryological counter-evidence 
established by the agreement between the independent investigations 
of Röse and TARKER? 
+) 10 
Fig. 3. Evolution of the Human Upper Molars. 9 Anaptomorphus, a lower eocene 
monkey. 10 An upper eocene monkey. 11 and 12 Human, 11 Esquimaux, 12 negro. 
See addition of “talon”, hy to “trigon” composed of pa, pr, me. 
This is also, I believe, explained by a study of the fossil forms. 
As we have seen in the most primitive types the protocone was the 
most prominent cusp in both jaws, but in course of later development 
of the upper molars, during the cretaceous and eocene periods, the 
protocone was depressed to the level of the paracone and metacone 
(see the primitive Carnivora, Creodonta and Insectivora). On the 
other hand in the lower molars, the protoconid retained its relatively 
prominent position and size. If the ontogenetic development of the 
lower molars corresponds with the ancestral order, it is probably 
because the relative primitive position of the cusps was conserved ; 
whereas in the upper molars, in which there is less correspondence, 
it was lost. I find in the lower eocene Ungulates that the paracone 
