SEMICIRCULAR CANALS AND THE VESTIBULE. 391 



cyst in place of the usual grains of sand. When now a magnet was 

 brought near to the animal reactions were obtained which showed 

 that the pressure of the iron upon the hairs influenced its position. 

 The position taken by the animal under these conditions was such 

 as would be expected as a resultant of the forces of magnetism and 

 gravity, and the experiment, therefore, justifies the hypothesis that 

 under normal conditions gravity affects the otoliths and through 

 them the muscular co-ordination of the animal. These experiments 

 have been confirmed by Prentiss.* This author has shown, 

 moreover, that if larval lobsters (4th stage) are prevented from 

 obtaining otoliths after moulting by placing them in filtered sea- 

 water, their movements, like those of larvae deprived of their 

 otocysts, show a distinct instability and lack of normal orientation. 



* Prentiss, 'Bulletin of Museum of Comparative Zoology," Harvard, 

 1901, xxxvi., No. 7. 



