280 Dr. W. Kiikenthal on the 
Baume, like many other investigators, therefore regards as 
the original form a dentition consisting of numerous similar 
teeth, and consequently starts from the Edentates and espe- 
cially the Toothed Whales as the primary type; I therefore 
commence by examining the latter. 
TootHeD WuHaAtes: The 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 Phocena communis of nearly full time, 
I find 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 on 
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 Julinf, 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 the same time. 
My investigations in this direction so far embrace a con- 
siderable number of embryos of Beluga leucas, Globiocephalus 
melas, and Turstops tursio; this is what I have discovered : 
THE DENTITION OF THE TOOTHED WHALES IS A TRUE MILK- 
DENTITION, or, better, it belongs to the first 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 that 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 both 
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. 
WHALEBONE WHALES: The Whalebone Whales, for 
which, since they have genetically nothing to do with the 
Toothed Whales, I claim a special order within the Mamma- 
* Weber, ‘Studien tiber Saugetiere ’: Jena, 1886, p. 196. 
+ Ch. Julin, “ Recherches sur ossification du maxillaire inférieur, et 
sur la constitution du systéme dentaire chez le foetus de la Balenoptera 
rostrata,” Arch, de Biologie, 1880. 
{ Weber, op. eit. p. 154. 
