550 J. T. WILSON AND J. P. HILL. 
vorangegangen ist, darstellen konnen” (3, p. 91). The argu- 
ments used by Leche to dispose of the first view seem to us 
exceeding weak. ‘“‘Gegen die erste alternative spricht nun 
zunachst der Umstand dass dieselbe ohne jegliche Analogie 
bei den iibrigen Beutelthieren ist, denn bei diesen entspricht 
ja, wie die neusten Untersuchungen tibereinstimmend darthun, 
das persistirende Gebiss der ersten Dentition der placentalen 
Sdugethiere. Und da gerade Myrmecobius in Bezug auf die 
Anzahl der Backenzihne die primitivste Form unter den 
lebenden Beutelthieren ist, wurde, falls wir diese Alternative 
acceptiren wollten, das Myrmecobius-Gebiss durch das Vor- 
kommen einer ganzen Reihe von Zahnen der zweiten Denti- 
tion zugleich hoher als die tibrigen Beutelthiere entwickelt 
sein-eine Annahme, welche durch ihren Mangel an wahrschein- 
lichkeit von selbst fallt ” (8, p. 91). 
It is plain that the “general acceptance in Marsupials of 
the homology of the persisting teeth to the milk-teeth of Pla- 
centals’’ simply goes for nothing in the present connection, 
seeing that it is just the validity of this “general acceptance ”’ 
that is challenged, partly on the grounds of the existence of 
the “prelacteals.” To determine the latter as morphologically 
‘‘ prelacteal”? on the grounds of the accepted “ milk ” homo- 
logy of the persisting marsupial teeth appears to us like 
reasoning in the very narrowest of circles. 
And with regard to the second argument from the condition 
in Myrmecobius we are at a loss to perceive its bearing upon 
the question at issue. Granting for the present, at least, that 
Myrmecobius is the most primitive marsupial form, are we 
in the least bound to assume that even the most primitive 
mammal should exhibit partial monophyodontism, or at least 
incompleteness of its successional series? ‘To make such an 
assumption is again to beg one of the most important questions 
at issue. Why, we ask, should it not simply be held that the 
most primitive mammals possessed both a milk and a succes- 
sional tooth series, but that the former had undergone almost 
total suppression amongst the ancestors of the modern Marsu- 
pials (? Triconodon). We have already pointed out that the 
