DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 951 
retention of the single tooth-change from Mesozoic times to 
the present offers neither more nor less difficulty than any 
other mode of explaining the Triconodon condition (cf. also 
Leche [28], p. 278). 
The only argument used by Leche in this relation which 
appears to us to require serious consideration is his statement 
respecting traces of true “ prelacteal’’ tooth-rudiments labially 
from the milk enamel-organs of higher mammals.) But when 
we examine the descriptions and figures upon which Leche 
bases this startling statement, we find that the indications 
referred to are of the very feeblest and most inconclusive kind 
(see his figs. 3 and 5’). We have ourselves met with struc- 
tural indications in the pig (cf. figs. 83—85 ; text-figs. 2 and 
3) which at first tend to suggest, even more strongly than 
Leche’s, an interpretation such as he has given. But they are 
really to be explained in a quite different manner, as we hope 
to show incidentally later on when dealing with the question 
of molar homology (cf. p. 567, e¢ seq.). 
It is unnecessary here to recapitulate our own observations 
upon the so-called “ prelacteal”’ vestigial teeth in Perameles, 
which, in accordance with our theory, we have constantly 
designated as “milk ” or deciduous teeth. It is sufficient to 
say that we have recognised what we believe to be vestiges of 
these teeth in connection with at least four, and perhaps all, 
of the upper incisors, at least two lower incisors, and both 
upper and lower canines. Of these, d22, di+, and d< have 
been traced in the cupped and papillated stage, while di; 
becomes strongly and d; weakly calcified. 
In our examination of these interesting rudiments we very 
early became convinced of their serial homology with the 
tooth dp. 3. As we have stated in the introductory part of 
this paper, this conviction at first compelled us to take up the 
' The argument from the topographical relations between those portions of 
the dental lamina connected with the rudimentary and persisting teeth, 
respectively, may be passed over as unimportant. The various stages we 
figure of vestigial teeth in Perameles quite sufficiently explain any pecu- 
liarity in the late stages of the vestigial teeth, alone studied by Leche. 
