DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 549 
If now it be admitted, on the strength of our previous con- 
tentions, that the doctrine of the homology of the existing 
antemolar teeth of Marsupials to the Kutherian milk denti- 
tion rests upon very slender grounds, surely the discovery in 
Marsupials of vestiges of a dentition preceding the adult one 
may well give us pause before adding, with Leche, a theore- 
tical third to the two dentitions already recognised as the 
typical mammalian heritage. We do not think that due con- 
sideration has yet been given to the question whether these 
discoveries alone do not enable us to decide upon the precise 
value to be attached to the supposed rudimentary enamel- 
germs, in whose determination as such Leche has at least 
taught us to exercise a very cautious and even sceptical criti- 
cism, and which he himself after all accepts rather as poten- 
tial than as actual “ enamel-germs.” 
If these problematical germs can be dispensed with, the 
view of their successional homology proving to be ill-founded, 
the theory of the marsupial dentition may be reduced to very 
simple terms. The whole of the adult marsupial antemolar 
teeth (except dp. 3) could then simply be recognised as homo- 
logous to the permanent or successional teeth of other mam- 
mals; whilst the homologues of the Eutherian milk-teeth 
would be found in the deciduous premolar, together with any 
vestigial so-called ‘ prelacteal”’ teeth which may be recog- 
nisable. 
This now proposed explanation of the marsupial dentition 
has not been wholly ignored by Leche. Thus, in reference to 
the supposed “ prelacteals”? of Myrmecobius, he says, ‘‘ Ent- 
weder stellen die fraglichen rudimentéren Zihne die erste 
(Milch) Dentition dar, welche bis auf diese Reste ver- 
schwunden ist, wahrend die zweite Dentition, welche die erste 
wahrend der Phylogenese ganzlich ihrer Funktion enthoben 
und verdrangt hat, durch die persistirenden Zahne reprasen- 
tirt wird. Oder, die persistirenden Zahne entsprechen bei 
Myrmecobius wie bei den andern Beutelthieren der ersten 
Dentition, so dass die erwaihnten rudimentaren Zahne nichts 
anderes als Reste einer Dentition, welche der ersten Dentition 
