434 J- T. WILSON AND J. P. HUGE. 
predecessor. Kiikenthal’s claim was promptly admitted by 
Thomas himself (8) as apparently incontrovertible, and he 
therefore no longer refuses to subscribe to the view of a primi- 
tive diphyodontism of mammals, ‘‘ probably in direct suc- 
cession to the irregular polyphyodontism of their reptilian 
ancestors,”—a diphyodontism which “ may even have existed 
in what were in other respects members of the latter class.” 
Nevertheless Thomas is far from admitting that the whole 
problem of the phylogeny of the dentition in Mammalia 
is thereby cleared up. He regards, e.g., the fact that the 
Mesozoic Triconodon changed a single tooth only, as ren- 
dered inexplicable by the newer theory. Still he definitely 
adopts the latter, merely passing on to a criticism of Kiken- 
thal’s views upon other issues, i.e. the homologies of the 
individual premolars, and the questions of the nature and mode 
of origin of the molars. 
An important and elaborate memoir on the development of 
the human teeth by Carl Rose was published in 1891 (9), and 
apparently independently of Kiukenthal, and contempora- 
neously with him, Rése had also worked out the tooth develop- 
ment of Didelphys as well as of several other marsupial 
forms. The results of this work were published in September, 
18921) 2 
As regards the question of the presence of rudimentary 
enamel-germs of successional teeth, Rose largely confirms the 
observations of Kiikenthal upon Didelphys,” and he showed 
that lingual ingrowths of the dental lamina, similar to those 
found in Didelphys, were present in all other Marsupials he 
examined. 
During 1892-3 Rose continued to publish the results of an 
active investigation into the phenomena of tooth development 
in a number of other forms, both mammalian and reptilian. 
1 Rése’s views upon the marsupial dentition were, however, outlined in his 
paper on tooth development in Edentata, published in July, 1892 (34). 
2 An unfortunate error in Rose’s paper, subsequently acknowledged by 
him, was his mistaking the enamel-organ of the deciduous premolar for that 
of the first molar. 
