OBJECTIONS AND DIFFICULTIES AND OTHER THEORIES 



213 



protocone of the premolars, with the paracone of most molars, and with 

 the falsely called protocone of the molars of trituberculate Insectivores 

 and of the Jurassic genus jFVmA'.s/V.s (Fig. 204). Stated in another way 

 his conclusions are that, (1) the antero-extcrnal cone, or paracone above 

 and protoconid below, is the reptilian cone both in the molars and premolars, 

 a conclusion supported by the Danish observer Winge; 1 (2) the falsely 

 called protocone of the upper molars is borne on an internal ledge or 

 extension of the base of the crown of secondary origin; (3) the meta- 

 cone is a similar backward development of the paracone which rises very 

 early in ontogeny long before the protocone; (4) the evidence advanced 



ps. pa. me. mis. pg. ms. mis. 



ps. 



ruts 



FIG. 204. Shading illustrates Woodward's hypothesis of the homological relations of the 

 tritubercular, zalambdodont molar types of Centetes (A) and Chrysochloris (B) to the sexituber- 

 cular dilambdodont molars of Tnl/ia (C). The whole of the Ctntetc* molar is supposed to correspond 

 to the anterior outer portion of the Talpa molar, while the " hypocone " of the Chrysochloris molar 

 is homologized with the antero-internal portion of the crown of Talpa. The posterior half of the 

 Talpa molar is supposed to be a neomorph or secondary upgrowth of the posterior side of the 

 tooth. But according to Gidley's interpretation the single V in Centetes and Chrysochloris is 

 secondary and represents the fusion of the two V's (pa, me) seen in Talpa. 



The abbreviations are incorrect. For true interpretation see p. 225, Addendum. 



in support of the tritubercular theory is insufficient to prove that the 

 upper molars primarily evolved on the lines of that theory; (5) owing 

 to want of material trituberculists have been led to assume that the 

 upper molars of the early mammalia passed- through similar stages to 

 those which they have determined for the lower teeth, and consequently 

 they have in most cases incorrectly identified the primary cone: (6) 

 that as regards the actual primary cone (paracone above, protoconid 

 below), its ontogeny recapitulates its phylogeny. 



Ontogenetic Order according to Marett Tims. 



Dr. F. W. Marett Tims ' 2 has reached partly identical conclusions 

 chiefly from the embryology of the teeth of the dog, namely, that the 

 cheek teeth of the dog are composed of 



(1) A Primary Cone = paracone of ms, protocone of pms protoconid 

 of lower ms and pms. 



ll '0m Pattedyrenes Tandskifte isaer med Hensyn til Taendernes Former." Vul<n-l.-. 

 Meddel. fra den Xaturh. Fortn. i. Kjoheiiharn, 1SS'2, p. 15. 



2 "On the Tooth-genesis of the Canidiv," Jour. Linn. Soc., Vol. XXV., Zoo!., No. 164, 

 1806, pp. 445-480. 



