20 



FRANK E. BEDDARD 



generalization too far to regard the (? same) outgrowths of this 

 embryo of Physeter as a rudiment of a milk dentition when 

 they appear on the labial side and of a postpermanent genera- 

 tion when they are processes of the lingual surface of the dental 

 lamina. There are, however, as it appears to me from the facts 

 represented in my sections, and from the literature briefly 

 referred to above, considerable grounds for believing these 

 outgrowths of the dental lamina in Physeter to represent 



TEXT-FIC4. 12. 



Three sections at an interval from each other of one section only, 

 nearer to the anterior end of the upper jaw than those sections 

 represented in preceding figures, and therefore at the most 

 complete stage of development shown in the foetus examined. 

 They show certain differences from the more posteriorly situated 

 sections of the upper jaw series. This chiefly affects the relative 

 positions of the milk rudiment (a) and the residual lamina (c) to 

 each other and to the germ of the permanent tooth (6) (assuming 

 that these several outgrowths are cori'ectly identified). 



vestiges of a milk dentition which never comes to maturity, 

 and that the permanent teeth of this cetacean are therefore 

 to be looked upon as the equivalent of the permanent dentition 

 of other mammals. This conclusion is not that of Kiikenthal 

 (2), who, however, did not (probably was not able to) refer to 

 the memoir of Bouchet and Beauregard owing to nearly simul- 

 taneous publication. 



