716 



a successor, in the same way as happens in the Monodelphian 

 mammals with all tiie milk-teeth. 



The opinion tiiat the dentition of Marsupials corresponds with the 

 second set uf teeth of the Monodelphians was generally held until 

 about 1890, when in a comparatively short time it gave way to 

 a different view. It was namely at that period that ontogenetical 

 researches came more to the fore and led not only to a change in 

 the conception about the Marsupial dentition, but also introduced new 

 ideas into odontology, which were the starting-point for so much 

 capriciousness in the interpretation of the phenomena and caused so 

 much diversity of opinion that in the casuistic literature on the onto- 

 genesis of the Marsnpialian dentition one finds the different authors 

 continually at variance; as soon as detailed questions are dealt with 

 there is hardly any agreement. This period in the history of odonto- 

 logy begins with the papers Kükenthal, Lechk and Rose. Especially 

 the researches and views of the first of these authors were of para- 

 mount importance for the new course. 



However much these authors might differ in other respects, they 

 agreed on the point that the functionating dentition of the Marsupials 

 must be considered to correspond to the milk-dentition of the Mono- 

 delphians. And as to the tooth which precedes the first molar and 

 is replaced, it should be looked upon as a milk-tooth which is replaced 

 by the only developed tooth of the permanent dentition. In short, 

 while in the opinion of the older anatomists Marsupials only possess 

 the second set of teeth and of the first only temporaril}' a single 

 tooth, this opinion is reversed after 1890 : Marsupials possess only 

 the milk-set and of the second one only a single tooth develops. 

 For KtJKENTHAL and Rose this tooth was the remnant of the lost 

 dentition, for Leche on the other hand it was the first element of 

 a new series of teeth, attaining full development in the Monodelphians. 



When investigating the development of the dentition of a Marsupial, 

 preferably of a Polyprotodont, without being biased by existing 

 theories, one cannot help wondering a little at the weakness of the 

 grounds on which Kükenthal based his theory, the more so since 

 on a premise against which many objections might be raised he 

 wanted to introduce an entirely new conception into mammalian 

 odontology, a conception which made its confusing influence felt 

 over the whole range of this department of science. This conception 

 is the so-called prelacteal dentition. As such this author distinguishes 

 a dental series \vhich would precede the milk-teeth series. Hence 

 we should have to distinguish in mammals at least three dentitions : 

 the prelacteal, the lacteal and the permanent one. Of these three the 



