440 J. T. WILSON AND J. P. HILL. 
In Myrmecobius Leche had discovered the presence of 
calcified structures connected with the dental lamina, and 
placed labially with reference to it and to the enamel-germs 
of the adult teeth. These calcified tooth-remains, though less 
perfectly formed, or perhaps we should say more completely 
degenerated, than those described by Mr. Woodward, bear a 
striking general resemblance to his, both in respect of their 
topographical relationships and of their structural features. 
Leche’s interpretation of them was, however, widely different 
from that given by Woodward in the case of the Macropod 
vestigial teeth, for he viewed the calcified structures as the 
sole remains of an entire “ prelacteal” dentition which had 
otherwise become suppressed. To this view Leche still 
adheres in his latest work (3), where he claims that both 
Woodward’s and Rose’s observations just referred to are to be 
explained along similar lines. 
Woodward himself (14) has accepted Leche’s notion 
of a “prelacteal” dentition, so far at least as Myrmeco- 
bius is concerned, and he believes that he has obtained 
confirmation of the view through a similar discovery in 
Phascologale. 
By far the most important recent contribution to the lite- 
rature of this subject is the comprehensive monograph by 
Professor W. Leche already referred to (3). 
In addition to a rich collection of observations copiously 
illustrated, this book contains a systematic discussion of all 
the more important issues raised by a study of the ontogeny of 
the mammalian dentition. In the latter portion of this paper 
Leche’s views are dealt with in detail in so far as they have a 
bearing upon the subject-matter of this work. Meanwhile we 
may remark that one of the most important features of Leche’s 
contribution is his criticism of the commonly prevalent but 
loose and unreliable notion as to what really constitutes a 
morphological tooth-germ. 
Such a critical determination is urgently needed if any 
further progress is to be made in investigation of the dentition 
along the lines of embryological research. In the development 
