( 789) 



witli tlie Orang and Gorilla. Moreover Zückerkandl ') has shown 

 that the epithelial rudiment of a fourth molar of man is formed 

 with the majority of the individuals. This rudiment of a tooth 

 and the eventual eruption of the fourth molar were till now 

 phenomena which were somewhat difficult to interprete. There 

 was an inclination to keep this fourth molar with man for an 

 atavism and the set of teeth of man was deduced from a hypo- 

 thetical primitive form when the set of teeth cont^iined four 

 molars. Here however the difficulty offers itself that among the 

 already numerous well known primitive Primates there has never been 

 found a form with four molars. Zuckerkandl also reveals this difti- 

 culty where he points to it that four molars should onl^' appear with 

 the primitive forms of the carnivores. Selenka '') also, Avho found from 

 his rich material that with Orang in 207„ of the cases appears a 

 fourth molar feels the mentioned difficulty and interprets the 

 variation in another way. It should not be atavism but a progressive 

 phenomenon in that sense, that the set of teeth of Orang is on the 

 way of bringing into development a fourth molar. It appears to 

 me that this explanation of Sei.enka is not correct. If this variation 

 Avere only known to us from Orang, no direct difficulties could be 

 stated against this hypothesis. But such a fourth molar also occurs 

 as I said before very often with man. And Jiow it is not doubtful 

 that the extremity of the human set of teetii is in a state of regres- 

 sion, the third molar is always more or less I'educed and even 

 according to the investigations of de Terra ') and others issues no 

 more with at least 12 7o of the recent Europeans. Where it 

 is now fixed that our set of teetli reduces at its extremity, the 

 formation and issue of a fourth molar can hardly be interpreted as 

 a progressive phenomenon. 



The hypothesis brought forward by me gives a simple solution 

 of the difficulty. The fourth molar of man and of the Anthropoids 

 is indeed an atavism but does not refer back to a removed primi- 

 tive form unknown to us, but does not go any farther than to the 

 nearest past of the history of development of our set of teeth, it 

 is the homologon of M, of the Platyrrhines. And contemplated in 

 such a way the relatively frequent occurrence of it can no longer 

 surprise us. 



I) E. Zuckerkandl, Viertcr Malilzalin beim Menschen. Sitzungsber. der k. Akad. 

 d. Wiss. Wien Bnd. G. 



^) E. Selenka. Meusclienaffen. Rassen, Scbadel und Bezahnung des Orang Utan. 

 Wiesbaden 1898. 



3; M. DE Tehra. Beitriige zueinerOdonlographie der Menschenrassen. Zurich 1905. 



