546 CHORD AT A, 



never replaces the functional teeth ; hence these latter are 

 often regarded as the milk-teeth {cf. Metatheria). The homo- 

 dont condition is correlated with the function of seizing and 

 retaining small slippery fish which are not masticated but 

 *' bolted " entire, as in the case of sharks and other fish. The 

 immense number of teeth is a great morphological dif^culty, 

 especially if we assume that the Cetacea are descended from 

 terrestrial Eutheria^ with teeth approximating in number 



Fig- 377.— Diagrammatic Section of Stomach of Porpoise. 



(After Flower and Lyddeker.) 



^, Bile-duct, g. Duodenum. _/^ Pylorus, e^ Pyloric Portion, c, Middle 

 Portion, b^ Cardiac Part, a, (Esophagus. 



to the typical dentition of f ytI • ^^ ^^^s been suggested 

 that the tritubercular or multitubercular carnivorous type 

 of tooth of these ancestors, losing its tearing and crushing 

 function, became split up into three or more single-cusped 

 elements which would give at least f :t:tI."I"! ^^ f I- The 

 rudimentary molar teeth of the Mystacoceti or toothless 

 whales are said to break up in this way into simple elements. 



