554 J. T. WILSON AND J. P. HILL. 
so-called ‘ prelacteals,” 
teeth. 
Along with these considerations may be borne in mind the 
tendency, so often illustrated amongst Marsupials, for this 
same tooth to share the fate of its fellows and to become 
vestigial. We have referred in the introduction to its con- 
dition in Dasyurus and Phascologale, and here we need 
do no more than refer to our figures of the tooth in the first- 
named of these forms (figs. 80 and 81). 
On the grounds, therefore, both here and elsewhere detailed, 
we can have no hesitation in affirming that dp. 3 ought to be 
regarded as a member of the same series which includes the 
vestigial canines and incisors, and that this series corresponds 
to nothing else than the normal mammalian milk-series, which 
in Marsupials has been profoundly modified in the way of 
suppression. 
and not to the permanent antemolar 
Primitive Diphyodontism and “Suppression.” 
Along such lines of reasoning we thus reach the standpoint 
of the primitive diphyodontism of mammals—a_ position 
already occupied, though, as we believe, on erroneous grounds, 
by Kikenthal, Rose, and others. We believe that we are 
justified in seeking for the cause of the almost total suppres- 
sion of the milk-teeth in front of the last premolar, in the 
modified condition of the mouth in marsupial young in con- 
sequence of its peculiar adaptation to the sucking function. 
This would seem to be a more natural employment of this 
factor than that of Leche, who has already suggested it. For 
he seeks by it to explain the non-appearance of an entirely 
new series of replacing teeth. Surely such an organic 
modification would more immediately tell upon an existing 
milk dentition in the way of suppression, rather than— 
merely through delay of such dentition—affect the subsequent 
development of successors. 
In fact, Leche himself, in opposing the view that the second 
dentition has actually once been present and has since dis- 
appeared, contends in so many words that, according to the 
