56 A BOOK OF WHALES 



these several characters are seen in a condition inter- 

 mediate to that which obtains in the purely land animal 

 on the one hand, and in the purely aquatic whales 

 on the other. And, furthermore, in the Manatee, 

 which, if it be an ally of the whale, can hardly be re- 

 garded as an ally of the carnivora (to which group, 

 of course, the otter and the seal belong), there is 

 the same obliquity of the diaphragm. Thus in three 

 types, the whale, the manatee, and the seal, we have 

 the same series of modifications existing-. If the 



o 



whale is a relative of the manatee, it is not of the 

 seal, so that any renewed attempt to urge the argu- 

 ment from affinity fails. As to the obliquity of the 

 diaphragm being due to the reduction of the sternum, 

 this is disproved by several instances among the 

 whales. In Beluga the diaphragm is attached to 

 the sternum before its end ; in Hyperoodon the same 

 is the case ; while in Balcenoptera the attachment is 

 altogether behind the sternum. There is thus no 

 special relation to be observed between the end 

 of the sternum and the ventral insertion of the 

 diaphragm. 



Moreover, as showing that it is a modification of 

 a recent kind, it is interesting to notice that in the 

 porpoise of the youngest stage that has been 

 observed the relative proportions of the ventral and 

 the dorsal line of the thoracic cavity are as i : 175 ; 

 while in the adult the same proportions are as i : 2*25. 

 Thus these peculiarities are developed quite late, 

 showing that they are a recent acquisition, and 

 tending therefore to prove that they are developed 



