( 790 ) 



More direct proofs may however be cited for the conclusion that 

 31, of the Platjrrhines should be reduced. For if the sets of teeth of 

 different representatives of this group are investigated, it is undeni- 

 able that Mi is behind in development to J/, and M^. 



Not all Platyrrhines are alike in this regard, with some species the 

 set uf teeth is apparently very constant with other it is more varia- 

 ble. A particularly fixed set of teeth CInysotlirix seems to possess. I 

 could at least lind not a single deviation in the 130 skulls of Chry- 

 sotlirix sciurea which I possess, no more in GO skulls of Cebus fatuel- 

 lus, although the M^ is already very much reduced with this species. 

 Ateles on the contrary seems to possess a set of teeth which is 

 richer in variations and Bateson ') mentions three cases in which 

 the M, which is already reduced in this genus quite fails. The men- 

 tioned author points to it that in these cases Ateles possessed a 

 formula for its set of teeth which is typical for the second family 

 of the Platyrrhines — the Hapalidae. And in connection with this 

 I may now examine the set of teeth of the Hapalidae in the 

 light of my iiypothesis. This hypothesis puts that jM, of the Pla- 

 tyrriiines became lost in passing to the catarrhine type, that m, 

 becomes il/j and that 1\ no longer issues. Where a reduction 

 of M, is not seldom found with the Cebidae, and now and then 

 even it is quite wanting as an individual variation, there M' is 

 already constantly absent with the Hapalidae. So with these Pla- 

 tyrrhines one phase of the process has already been run through, 

 but not yet the second phase, the progression from m, to AI^. So 

 according to my opinion the set of the Hapalidae does not stand 

 as a deviating form at the side of that of the other Platyrrhines, 

 but must be considered as an intermediate form, between the original 

 piatyrrliine atid the definite catarrhine set of teeth. 



So we see that several i)henomena plead for my opinion, that the 

 catarrhine set of teeth has not originated by an excalation but by a 

 terminal re(kiction, and I must stop at my assertion that, because 

 ///, lias become M^ the replacing tootii, wiiich originally belonged 

 (o it, i.e. J\ no longer appears. 



By this supposition, the observation of the anthropologists is done 

 justice to, that a rudimentary tooth does relatively often appear with 

 man and Gorilla between P, and M^. When P, has only been sup- 

 pressed as a normal element of the set of teeth, in a relatively recent 

 period of the development, than the supposition lies at hand, that this 

 .tooth also like M, of the Platyrrhines ontogenetically will be formed 



1) W. Bateson. Materials for tlie Study of Variation. London, 1S94. 



