540 



Woodward (4) has described vestigial calcified milk predecessors 

 to ^ , p^ , ~c and ^ in Erinaceus and also an uncalcified vestige 

 to ^. The remaining teeth have f u n c t i o n a 1 predecessors. He con- 

 firms Leche's latest conclusion that the adult incisors, canines and 

 premolars belong to the replacing (3"^) set; that indications of three 

 dentitions were observed in the molar region, representing the milk 

 (2°'^), replacing {S'^} and a post-permanent (4^'0 set of teeth, the mo- 

 lars being referred to the S'^ or replacing dentition. 



Through the kindness of Mr. Woodward I have had an oppor- 

 tunity of examining these sections also, and I entirely agree with his 

 interpretation of these facts. But on comparing these with sections 

 of the teeth in Dasyurus and with Leche's figures of the condition 

 found in Myrmecobius, they appear to me to be precisely similar. 

 Why in the one case should the dentitions be referred to the 2""*, 

 3"^" and 4'^ and in the others to the 1^', 2'^'^ and S""-*? 



It would appear to me that the interpretation of the conditions 

 found in all these is the same, since the appearances are the same ; 

 and that the interpretation given in the case of Erinaceus is the 

 simplest and most in accord with the known facts of the dentition 

 in other animals, and therefore the most likely to be the correct one. 



The same, I believe, may be said of all the other cases at pre- 

 sent described, in which the pre-milk dentition is said to exist In 

 a recent paper KükenthalCQ) appears to doubt the existence of the 

 pre-milk dentition, but at the end of the same paper he apparently 

 contradicts himself and admits its presence. So far, then, I think 

 there are no sufficiently valid reasons for believing in its presence, 

 beyond the purely theoretical grounds of the possibility of its existence 

 at some former remote period, built upon the assumption of the poly- 

 phyodont ancestry of Mammals. 



The condition found in the Dog is as follows. Though I have 

 examined a number of jaws , varying in age from birth up to three 

 weeks, yet, in no single instance have I observed any trace of a pre- 

 milk dentition. On the other hand, the deciduous, successional and 

 post - permanent series are clearly to be made out. The last is most 

 marked in the incisor region (fig. 1) that is, in the very region, with 

 the certain exception of the canine, in which the pre - milk teeth have 

 been stated to exist. 



Turning next to the consideration of the first premolar tooth. As 

 is well known this tooth is present in one dentition only in the great 

 majority of Mammals, the more prominent exceptions being the 

 Indian Tapir (10) , the Hyrax and occasionally the Pig. (12). If the 



