ii2 LIFE OF FLOWER 



growth, and is not shed until all the other teeth are in 

 position and use. On the other hand, in the Tasmanian 

 wolf the temporary tooth is very rudimentary in size 

 and form, and is shed or absorbed before any other 

 teeth enter the gum. Anterior to the period of Sir 

 William Flower's communication, mammals had been, 

 in regard to the succession of their teeth, divided into 

 two groups the Monophyodonts, or those that generate 

 a single series of teeth, and the Diphyodonts, or those 

 that develop two sets of teeth, but, as he pointed out, 

 even in the most typical Diphyodonts the successional 

 process does not extend to the whole of the teeth, 

 always stopping short of those situated most posteriorly 

 in each series. The pouched animals (marsupials), he 

 stated, occupied an intermediate position, presenting, as 

 it were, a rudimentary diphyodont condition, the suc- 

 cessional process being confined to a single tooth on 

 each side of each jaw." 



All this is unexceptionable. Flower, however, went 

 further than this, and claimed that the true molar teeth 

 of mammals correspond serially with the permanent 

 premolars, canines, and incisors, and not with their 

 deciduous predecessors. And he therefore urged (as 

 indeed must be the case on these premisses) that the 

 whole dentition of adult marsupials corresponds with 

 the permanent dentition of placentals. A further infer- 

 ence from this is that the milk-teeth, instead of 

 being an original development, may rather be a set 

 superadded to meet the temporary needs of mammals 

 whose permanent set is of a highly complex type. 



To review the objections which have been raised 

 against these views would be entering on a very difficult 



