GEOTKOPISM IN ANIMALS 187 



compared with those on the dependence of movements upon 

 the ear. And so it happens that Aubert and Delage 1 

 acknowledge the latter relation, but do not, as it seems to 

 me, acknowledge the former. I myself do not doubt the 

 belief of Breuer and Mach 2 that the organs associated with 

 the permanent changes in the position of the eyeballs, in 

 movements of the head, lie in the inner ear; and I think it 

 probable, in further accord with these authors, that these 

 organs are more especially the otoliths. I therefore add the 

 following results, obtained in a large series of experiments 

 on the inner ear of the shark (Scyllium-canicula), principally 

 to show that my ideas of the importance of the inner ear in 

 the geotropism of the higher animals rest upon personal 

 observations. 3 



I. If the otoliths are removed (either with a pair of 

 forceps or a small sharp spoon) from a shark (Scyllium- 

 canicula) upon one side, say the left, the following changes 

 occur in the animal in its orientation toward the center of 

 the earth: 



1. The animal no longer swims, as does the normal, so 

 that its medium plane is vertical, but it has a tendency to 

 turn the left or operated side downward at an angle of from 

 20 to 50, or even more, with the horizontal. 



2. The same change in the orientation can be noticed 

 when the animal is lying quietly upon the bottom of the 

 aquarium. It then frequently lies resting upon the left 

 lateral fins, while the right fin often does not touch the 

 bottom of the dish. 



3. When the animal is in the normal primary position, 



1 AUBERT, Physiologische Studien uber die Orientirung (Tubingen, 1888). 



2 MACH, Grundlinien der Lehre von den Bewegungsempfindungen (Leipzig, 1875), 

 p. 110. 



3 In an addendum to his paper on the Functions of the Central Nervous System, 

 etc. (Braunschweig, 1888), STEINER describes his experiments on "the semi-circular 

 canals of sharks." This author has overlooked the fact that it is the function of the 

 inner ear to call forth compensatory motions and positions, and so has failed to 

 make observations on the geotropic functions of the ear. (See MACH and BREUER.) 



