DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 509 
which such tooth-germs would have been formed (Schwalbe, 
Kikenthal). 
(d) The molars are the lateral end-members of separate 
dentitions: thus, in man, the dentition of which m. 1 is the 
end-member lies between the first and second dentitions (Rése 
[later view]). 
The arguments mainly relied on by Leche for the establish- 
ment of the “ milk” affinities of the molars largely hinge 
upon that interpretation of the development of the antemolar 
teeth with which we are now sufficiently familiar. 
The presence of a residual dental lamina—when its distal 
portion is somewhat swollen, and especially when the sur- 
rounding connective tissue is somewhat condensed—has been 
liberally drawn upon by him to furnish proofs of the milk 
homology of the antemolar teeth. And, having been accepted 
as practically sufficient for that purpose, it is now utilised in 
establishing a like homology for the molars. 
There can be no doubt that the molar segment of the dental 
lamina in Marsupials does very constantly develop a well- 
marked and often thickened residual laminar downgrowth 
Opposite each tooth as a consequence of its differentiation from 
the parent lamina. Here, as elsewhere, however, the residual 
lamina is in each case directly and serially continuous, fore and 
aft, with the intermediate undifferentiated parent lamina; in 
other words, the residual laminar downgrowth does not ex- 
hibit discrete swollen portions, but is an elongated continuous 
band, more or less uniformly thickened towards its free distal 
margin. 
Value of the Molar Residual Lamina. 
No secure basis for the establishment of the dentitional value 
of the molars is afforded by the presence of this residual 
lamina. It might be hastily concluded that, with our definite 
opinion of the “successional” character of the persisting 
antemolar teeth, we are bound to attach the same value to the 
molars. But we are by no means compelled todo so. If 
the molars are to be regarded as homologous with any one 
