CHAP. Vl] THE DENTAL SYSTEM OF THE PRIMATES 277 



tooth-generation. This question of the criteria is still a matter of 

 discussion (v. infra, p. 291, footnote). Schwalbe emphasizes the 

 significance of the independence of the milk and the permanent 

 series as regards their original positions, and this independence 

 would seem to be extended to the other dentitions subsequently 

 discovered. A large part of the memoir is devoted to a discussion 

 as to whether the ancestral mammals had one or two dentitions, 

 but this part of the question is of course no longer relevant, except 

 as regards one point. For in drawing up a table of the several 

 schemes which have been devised to shew the originator's views 

 regarding the relations of the permanent to the milk-teeth, 

 Schwalbe shews that he regards premolar and molar teeth 

 as derived from conjoined elements from the two dentitions 

 ( v. infra, p. 295). Kukenthal has, I believe, shewn evidence of 

 such a coalescence in a special instance, but otherwise the subject 

 has not been finally decided. 



The history of the evolution of the several series is thus to a 

 large extent obscure : the general significance of the replacement 

 of one dentition by another must evidently be found in the 

 advantage therefore conferred on the animal, which is thus able 

 to bring series after series into use, as the preceding set is lost or 

 worn away. And whether two, or all four of the dentitions recog- 

 nizable in the Hominidae, are inherited from ancestors in the 

 reptilian phase or not, the general conclusion must be that the 

 multiple dentition has been inherited from polyphyodont ancestors, 

 and has subsequently been modified in accordance with the special 

 Deeds of this family of the Primates. 



(6) In the endeavour to explain the origin of the different 

 turn is of teeth, such as the incisor, canine, and molar series, in other 

 words in the attempt to render a clear account of the historical 

 development of the heterodont dentition, some investigators would 

 refer all the various forms of teeth back to a simple ancestral parent- 

 form; and the simplest form known is the conical 1 peg-like tooth 

 found repeated in series with practically no variation (homodont) 2 , 



1 It appears that ltiitimeyer first suggested that the conical tooth represents the 

 ancestral form, cf. Forsyth-Major, Proc. Zool. Soc. 1893. 



- Leche, Bibliotheca zoologica, 1895, demurs to the view that the homodont 

 condition is the original mammalian one. 



