024 J. T. WILSON AND J. P. HILL. 
I. Homology of Antemolar Teeth of Marsupials. 
In reference to the first question, it has already been pointed 
out that Flower (and formerly Thomas) held that the non- 
changing antemolar teeth of Marsupials answered to the 
permanent or successional teeth of the Eutherian orders. This 
determination was adopted with great unanimity up till the 
period of publication of Kiikenthal’s discoveries, even by those 
who dissented on other fundamental points from the Flower- 
Thomas hypothesis regarding the dentition of Metatheria. 
But from the time that Kiikenthal first recognised the per- 
sistence of somewhat swollen (‘‘kolbig ”) downgrowths of the 
dental lamina at the lingual sides of the developing teeth of 
Marsupials, these downgrowths have on every hand been re- 
garded as the true equivalents of the Eutherian successional 
series, and the entire theory of the marsupial dentition has 
accordingly been remodelled to suit the newer interpretation. 
Up to the present, so far as we know, not a single investigator 
has ventured to proclaim his dissent from the latter-day creed 
in this respect.1 
If, then, we proceed to inquire upon what foundation this 
belief is based, we find that it rests solely on the occurrence, 
in Marsupials, of the epithelial downgrowths referred to, taken 
along with the similarity of the latter (@) to the earliest known 
rudiments of successional enamel-germs in other mammals, 
and (4) to the earliest stage of the one successional tooth 
admittedly existing in the marsupial jaw. But the question 
cannot, we believe, be thus summarily disposed of. It must 
be subjected to a much more thoroughgoing criticism, such 
as is embodied in the very weighty and thoughtful discus- 
sion of the entire subject by Professor Leche in his recent 
monograph (8). 
In that work Leche has pointed out that, in order to decide 
in any given case whether a tooth belongs to one or other 
dentition, certain criteria have been employed whose worth 
and validity are of very different degrees. He attempts to 
1 But see addendum, p. 581. 
