ANATOMY. 301 



scendant of a smaller species of whale. The seal's 

 caudal feet move up and down as does the whale's 

 tail. Seals give birth to their young and suckle them 

 on land or on ice floes, but whales always stick to their 

 native element. A fossil may yet be found to throw 

 some light on the source of the whale's origin. The 

 manatee, or sea-cow, is first cousin to the whale, and 

 there may have been a nearer relationship between 

 them. The stroke of the tail is the same in both 

 creatures. The uncut teeth in the whale's under-jaw 

 indicate that it may have been a saltus from the sea- 

 cow, or from a great seal now extinct. 



How the nostrils of the whale were placed away 

 back on the head is not easy to explain, unless a need 

 in the organic world is followed by a modification in 

 its favor. While it rests or sleeps at the surface, the 

 nasal apertures are above water, and the animal 

 breathes like an ox, and does not spout. However, if 

 the waves slop over the openings, the water is blown 

 upward with considerable force. The holes are closed 

 with sensitive valves which open to air, but close 

 when touched by water. When the animal dives to 

 the depth of a thousand feet, the pressure on the 

 valves must be great, unless support counter-pressure 

 come from elastic air in the lungs. In fin-backed 

 whales we have a fishy feature in a mammal. We 

 can not see how the slightly useful fin could corne 

 through inheritance. Several varieties of cetaceans 

 get along without the dorsal fin. At best the append- 

 age can do no more than help poise the trunk in a 

 comfortable attitude. It does not seem that necessity 

 was at the foundation of the dorsal fin. 

 Biology looks to heredity, adaptability, and utility, 

 for alterations in structure and modifications of 



