560 J. T. WILSON AND J. P. HILL. 
dentition, as is likely enough, they may very well be equivalent 
to the milk series, as represented, e.g., by dp.3. For the pro- 
duction of a residual dental lamina, during the differentiation 
of the enamel-organ of a tooth from the parent lamina, for us 
neither involves nor excludes the belief that successors 
may or do arise from that residual lamina. In other words, 
the production of a residual dental lamina by the lingual side 
of a milk tooth-germ in itself does no more than guarantee the 
possibility of the origin from it of a true successional tooth, 
just as its presence by the side of the Anlage of a successional 
tooth involves the potentiality of the origin from it of a tooth of 
a post-successional dentition. . 
We may, perhaps, advantageously refer once again to the 
condition of the first molar in the early stages (11 and 111) of 
Perameles. It will be remembered that in Stage 11 that 
enamel-organ is already recognisable as such, and its stage of 
development, though slightly less advanced than dp. 3, is fairly 
on a par with that of the anterior milk-teeth (‘ prelacteals”’). 
Its papilla is just indicated. 
In Stage 111 the resemblance between dp. 3 and m.1, both 
in their stage and manner of development, is worthy of note. 
At the very least it may be urged that there is no prima facie 
case for assigning m. 1 to a different series from dp. 3. 
Woodwaid at first (2, p. 460) seems to have based his 
belief in the successional character of the molars upon his 
inability to discover in Didelphys, in the Macropodide, 
and some other mammals “rudimentary enamel-germs” or 
“HKrsatzleisten” at their lingual sides. And he attempted 
to explain away what he regarded as a “suggestion ” of such 
structures in Lepus and Talpa by a critical distinction 
which, thoroughly carried out in reference to marsupial develop- 
mental features, leads directly up to the main thesis of this 
work. Woodward in a subsequent paper (18) has fully re- 
cognised the existence of such lingual growths of the molar 
dental lamina in certain Eutherian forms, and in that connec- 
tion reconsiders the question of molar homology. He still 
inclines strongly to the theory of their successional character, 
