LOCOMOTION AND LOCOMOTORY ORGANS 



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Figure 56. A Humpback jumping clear of the surface. {Glassell, ig^j. 



aboard the French research-ship Calypso. All the films show that the tail 

 beats absolutely vertically about a point near the vent, i.e. roughly the 

 base of the tail (Fig. 62; cf. also Figs. 1 01-105). This is in perfect accor- 

 dance with the motility of the animal's body, for if we examine a dead 

 porpoise (Fig. 61) we find that these apparently so flexible animals have 

 an extraordinarily rigid trunk. The head is movable to some extent, but 

 the base of the tail forms a very distinct pivotal point. 



Fig. 61 illustrates that, in addition to this fulcrum, another one is 

 found at the base of the flukes. This agrees with the evidence of the films 

 analysed by Parry (1949), which show clearly that, as the peduncle of the 

 tail moves up and down, the flukes carry out related movements of their 

 own. In fact, without these movements, the whale would be perfectly 

 motionless, no matter how vigorously it beats the water with its tail. 

 Similarly, if we were to sit in a boat and simply beat the water with a pair 

 of oars, our boat could hardly be expected to move forward. Now, the 

 fact that the flukes keep beating behind the peduncle of the tail, causes 

 them to 'scull' at an angle to the peduncle in all positions of the tail, and 



