100 



\V H A L E S 



dolphin suspended in air, a method singularly unsuited to the study of 

 the animal's motion in its natural habitat. Stass greatly improved matters 

 by attaching a special vibrograph to the back of a dolphin which swam 

 while attached to the ship by a long rope (loo yards) (Fig. 60). The 

 research was directed by a scientific institute on the Black Sea, and it 

 appeared that the vertical beat of the tail was one and a half times as 

 great as the lateral beat. Still, even these investigations are not altogether 

 convincing, and Parry (1949) pointed out that certain defects in the 

 apparatus might easily have produced the lateral effect. 



The most reliable work about the swimming of dolphins is unquestion- 

 ably that based on underwater films of swimming Bottlenose and other 

 dolphins, and of a Pigmy Sperm Whale in Marineland Aquarium 

 (Florida). These films, of which parts have been incorporated into Rachel 

 Carson's film 'The Sea Around Us', show very clearly that the animal's 

 bodily movements are confined to the tail, which consists of the peduncle 

 of the tail and the flukes. The same conclusion can be drawn from 

 \Villiamson's film on underwater life, and also from the beautiful colour 

 film of the underwater movements of Sperm Whales and dolphins, taken 



Figure 57. A dolphin jumping tlurteeiijecl out oj tlie water. 



