34 6 TOOTH GERMS IN WHALEBONE WHALES CHAP. 



driven upwards by the forcible expulsion of air from the lungs. 

 But for the most part the water which is spouted is simply 

 condensed breath. 



Like some, but not all, other aquatic Mammalia the Whales 

 have apparently no external ear. Indeed the opening of the ear 

 is excessively small. In a huge Eorqual it will " admit a quill " ; 

 and although " a quill " is rather vague, we may fairly allow any 

 sized quill without proving that the orifice of the auditory 

 passage is anything but exceedingly minute. As a proof, added 

 to so many, that the Whales are the progeny of terrestrial creatures, 

 we have the occasional traces of external ears. 1 



FIG. 182. Left lower jaw of foetus of lialaenoptera rostrata. Inner aspect, 

 natural size, showing teeth. (After Julin.) 



Whalebone Whales never possess permanent teeth as well as 

 the baleen ; but in the foetus are more than traces of true teeth, 

 which, however, never arrive at maturity. The whalebone itself is 

 described later (p. 354). That the Whalebone Whales possess teeth 

 while in the foetal condition was discovered so long ago as 180V. 

 It has since been confirmed by many observers. Not only is there 

 one set of teeth developed in the foetal Balaenoptera but two, 

 of which one comes to a greater maturity ; the other, in fact, 

 remaining at a very early stage of development. The more 

 complete dentition belongs to the milk series, as is the case with 

 the Toothed Whales. A very interesting conclusion with regard 

 to the derivation of the simple conical teeth of Whales seems to 

 follow from the development of these structures in Balaenoptera. 

 There are in the young foetus fewer teeth than in the more 

 advanced embryo. Now in the younger embryo some of the 

 teeth are furnished with more than one cusp ; they are bi- or 

 even tri-conodont. As Sir E. Owen observed, the teeth some of 



1 These have heen recorded by Professor Howes in the Porpoise. 



