THE EXTERNAL FORM OF WHALES 7 



THE TAIL 



The " flukes " of the whale, which form its tail, are 

 set, as everyone knows, at right angles to the plane 

 of the body, and not vertically as in fishes. It has 

 been noticed by several that the two halves of the 

 tail fin have surfaces which are not precisely parallel 

 to each other. They have, in fact, a screw-like form 

 one half being convex upwards, the other concave ; 

 and the use of the flukes seems to imply such a confor- 

 mation. Captain Scoresby observes of the Greenland 

 whale that it is "by means of the tail principally that 

 the whale advances through the water. The greatest 

 velocity is produced by powerful strokes against the 

 water, impressed alternately upward and downward ; 

 but a slower motion, it is believed, is elegantly pro- 

 duced by cutting the water laterally and obliquely 

 downward, in a similar manner as a boat is forced 

 along, with single oar, in the operation of sculling." 

 It is the latter motion, of course, that would be 

 brought about by the slightly screw-like form of the 

 tail fin. The tail, however, is also used in balancing, 

 as a whale when dead falls over on its side. They 

 are also of service in turning --and indeed as a 

 weapon of offence for striking boats. This seems to 

 be deliberate in the case of the Californian whale. 

 (See p. 170.) 



A dissection of the tail shows a beautiful and 

 elaborate complex of tendons, which are attached to 



* Dr. MURIE (Proc. Zool. Sac., 1865, p. 210) says the same of a living 

 porpoise at the Zoological Society's gardens. 



