280 Dr. W. Kiikentlial on the 



Baume, like many other investigators, therefore regards as 

 the original form a dentition consisting of numerous siinihir 

 teetli, and consequently starts from the Edentates and esp.i- 

 cially the Toothed Whales as the primary type; I therefore 

 commence by examining the latter. 



Toothed Whales : Tiie Toothed Whales are very gene- 

 rally considered as homodont; Weber*, however, is right in 

 considering the tusk of the Narwhal and the lower canine of 

 the Ziphioids to be vestiges of a former dissimilarity of denti- 

 tion. In an embryo of P/iocauia communis of nearly full time, 

 I iind a heterodont dentition tolerably sharply marked, since 

 out of the twenty-five teeth in each half of the jaw, the pos- 

 terior seven have two and sometimes three cusps. 



If on the one hand it is open to doubt whether the Toothed 

 Whales have an entirely homodont dentition, nevertheless o;i 

 the other it has been regarded as an absolutely certain fact 

 that the Toothed Whales are monophyodont, and that the. 

 single series of teeth which appears belongs to the permanent 

 dentition. Weber, who adopts afresh an idea previously 

 expressed by Julint, is alone in suggesting the hypothesis f, 

 that the dentition of the Toothed Whales comprises both 

 series of teeth, which, owing to the enlargement of the jaws, 

 ■were all able to appear at tlie same time. 



My investigations in this direction so far embrace a con- 

 siderable number of embryos of Beluga leucas^ Glohiocephalas 

 melas, and Tursiops tursio ; this is what I have discovered : 

 The dentition of the Toothed Whales is a true milk- 

 dentition, or, better, it belongs to the Hrst dentition, which 

 is permanent. Irrefragable proof of this is furnished by 

 the appearance of rudiments of second teeth internally to 

 those which persist ; it is true tliat the former are consider- 

 ably smaller and do not reach the surface, but they neverthe- 

 less possess a distinct crown of enamel, and even the charac- 

 teristic enamel pulp. 



In the Toothed Whales, therefore, the germs of bot'i 

 dentitions are found, and this cuts the ground from beneath 

 those hypotheses which start from them as typical monophyo- 

 dont animals ; Weber's hypothesis, also, is no longer tenable. 



WiiALEiJONE Whales: The Whalebone Whales, for 

 which, since they have gcncti(!ally nothing to do with the 

 Toothed Whales, I claim a special order within the Alamma- 



• AN'cber, ' Studien iiber Siiugetiere ' : Jeua, 1886, p. 190. 



t Ch. Jiiliii, " Ivecherches sur I'ossiiication dii mtixillaire infiMunir, et 

 sur la consiitiitioii du systome deiitaire chez le fLVtus do la liuUfnoptcra 

 rosfrfffa,^' Arch, do Bioloi^-io, 1880. 



I AVeber, op. cit. p. 134. 



