DEVELOPMENT AND SUCOERSSION OF TEETH IN PERAMELES. 448 
influence of the ruling theory of the homology of the perma- 
nent marsupial dentition to the milk dentition of higher 
Mammals, that it was some little time ere it occurred to us 
even to call in question the grounds of this identification, and 
at the same time the “ prelacteal”’ character of the vestigial 
teeth so frequently met with in Marsupials. But we very soon 
saw that, could the lacteal theory of the permanent mar- 
supial dentition be successfully impeached, all difficulties 
would be at once removed from the theory we felt bound to 
advocate from a consideration of the condition in Perameles, 
where the deciduous premolar and the so-called “ prelacteals ” 
evidently belong to one and the same dentitional series. This 
series would of course no longer be regarded as “ prelacteal,” 
but as the true homologue of the milk series of the higher 
Mammalia. 
It was while in this mental attitude to the question that we 
were first appealed to by Leche’s sceptical critique (3, pp. 132, 
136, &c.) of the criteria usually relied upon as sufficient to deter- 
mine whether or not any given lingual downgrowth of the 
dental lamina is morphologically the enamel-germ of a 
replacing tooth. For the fuller elaboration of our final 
attitude to the questions thus suggested, and for the evidence 
upon which our conclusions are based, we must refer to the 
subsequent sections of this paper. Here it is only necessary 
to say that we have been led to reject the presently prevailing 
Opinion regarding the more or less swollen downgrowths 
formed at the lingual sides of the developing marsupial teeth. 
It is our emphatic opinion that these are not the repre- 
sentatives of the replacing teeth of higher mammals, nor, 
indeed, are they actual individual tooth-germs at all, but mere 
residual appendages of the lamina, though they may, in a 
sense well recognised by Leche, contain the “ promise and the 
potency” of a possible tooth-generation. But the adult teeth 
in front of the last premolar are the genuine homologues of 
the replacing teeth of higher mammals, and the milk-teeth of 
the latter are represented, in front of the deciduous premolar, 
by the so-called “ prelacteal” vestiges, of which, as we shall 
