444 SCIENCE PROGRESS. 



he has proved the diphyodont condition of the Edentata, 

 and in Dasypus he has described three additional anterior 

 vestigial teeth. But he is surely in error when (29, 403-4) 

 he states that the similarity between the dentition of the 

 cetacea, edentates and marsupials is due to the persistence 

 of the first dentition, for the succession, as determined in 

 Tatusia by Rapp, Kraus (46), Gervais (36), Flower (25), 

 Tomes (24), and in Orycteropusby Thomas (14), shows that 

 it is the milk or first dentition which is transitional, although 

 in the first-named genus it may persist for some time as 

 a series of functional and rooted teeth while the adult denti- 

 tion is undoubtedly the replacing or second set. In the mar- 

 supials (27) he showed for the first time, by the discovery 

 of an almost complete series of rudimentary germs of a 

 second set of teeth, that the permanent dentition with the 

 exception of the one replacing tooth is a persistent milk 

 dentition. He has thus unconsciously revived, after a lapse 

 of twenty years, Owen's conclusions on this question, defi- 

 nitely showing that the milk dentition is not of secondary 

 origin, but at least of equal antiquity with the replacing 

 one ; and his ultimate conclusion is that the two sets of 

 teeth are to be regarded as sister dentitions. 



Rose (30, 31), who had been working at the development 

 of the teeth in the human subject previous to the appearance 

 of Kukenthal's views, took up this new departure with great 

 energy, and has since published about twenty papers deal- 

 ing with the detailed development of the teeth of mammals, 

 reptiles and fishes. Among the marsupials (3-), to which 

 he has largely devoted himself, he has confirmed Kuken- 

 thal's conclusions, but he considers that the last incisor, in 

 addition to the replacing premolar, is to be referred to the 

 second dentition, a view which I have endeavoured to show 

 is incorrect, as the tooth has the same relations as the 

 anterior incisors, which are undoubted milk teeth (12). 

 His work on the development of the human teeth (30, 31, 

 32) forms a most complete memoir of that subject, as also 

 does that on Didelphys (32). 



In his description of the dentition of the wombat (t,^) 

 Rose figures what he considers to be a rudimentary milk 



