76 A BOOK Of- WHALES 



now not the least doubt that the Dolphins are truly 

 diphyodont mammals, thus conforming' in a very 

 important character to their terrestrial allies. But 

 it is not quite settled which of the two dentitions it 

 is that persists. It is held by Kiikenthal that the 

 dental series of whales belongs to the milk dentition. 

 Thus the whales are clearly descendants of purely 

 diphyodont mammals. 



We have now to consider the whalebone whales, 

 which, in the adult condition, have no teeth, only the 

 plates of baleen, which will be treated of on another 

 page (p. So). As long ago as the year 1807 Geoffroy 

 St. Hilaire discovered the rudiments of teeth in a 

 fcetus of the Greenland whale, Balcena my slice tus ; 

 and this important discovery was afterwards confirmed 

 by the great Cuvier, as well as by his less-known 

 brother, Frederick Cuvier. Since then the facts have 

 been confirmed by others. (PI. VI.) 



The first discoverers of the facts contented them- 

 selves with little more than a statement of them. But 

 later Professor Julin laid great stress upon the ad- 

 ditional fact that the teeth of Balcenoptera rostrata 

 which he examined were not merely simple conical 

 teeth, but of a more complicated pattern ; he found 

 teeth with one cusp (like those of Cetacea generally), 

 with two, and even with three cusps. The simple 

 teeth, moreover, were those in the anterior part of 

 the jaws, the more complicated teeth further back. 

 In fact, there is an obvious likeness to a set of in- 

 cisors, followed by the more complicated cheek teeth. 

 This arrangement is typical of mammals, and is found 



