LIFE OF FLOWER 113 



question, and one in regard to which uniformity of 

 opinion by no means exists among naturalists even at the 

 present day. It may be mentioned, however, that from 

 the circumstance of the later milk-premolars resembling 

 (as was noticed by Flower in the case of the one tooth 

 replaced in marsupials) the true molars rather than the 

 permanent premolars, it has been suggested that the 

 milk-dentition is serially homologous with the true 

 molars. And on this view, the entire dentition of 

 marsupials (with the exception of the one replacing 

 tooth) corresponds to the milk-dentition of placentals. 

 Possibly, however, the larger number of incisors which 

 distinguish many of the carnivorous marsupials from the 

 placentals may be due to the development of teeth 

 belonging to the permanent series with those of the 

 milk-set, and both persisting together throughout life. 

 Be this as it may, it is evident, on the above view of 

 the serial homology of their dentition, that marsupials, 

 instead of as Flower supposed, showing the commence- 

 ment of a milk-dentition, really exhibit the decadence 

 of the permanent series. 



In this respect they display a precise similarity to the 

 modern elephants, as indeed was pointed out by Flower 

 in his original paper, although on a false premiss, for 

 he at that time regarded the anterior cheek-teeth of the 

 elephant as the representatives of the permanent pre- 

 molars, whereas they really correspond with the milk- 

 premolars. 



One objection has indeed been raised with regard to 



the identification of the adult marsupial dentition with 



the milk-set of placentals, namely, the existence in certain 



marsupialia of rudimentary teeth belonging to an earlier 



H 



