GEOTROPISM IN ANIMALS 189 
phenomena described under I are observed, only in a greater 
degree. If both auditory nerves are cut the phenomena 
described under ITI set in. 
V. If the otoliths are removed from one side and the 
auditory nerve is cut upon the other, the animal behaves as 
those described under II; with this difference, however, that 
the eyes of the animal are turned about the longitudinal 
axis of the animal toward that side where the auditory nerve 
is cut. 
Also, as regards the so-called forced movements — which 
are not considered in this paper—the animal behaves as if 
it had been operated upon only on one ear, namely, that whose 
auditory nerve is cut. 
VI. A shark whose head has been cut off, and which, as 
is well known, still swims, is no longer forced to assume a 
definite orientation toward the center of the earth. When 
laid upon its back it no longer attempts to reassume its 
accustomed position with its ventral side downward. 
The disturbances in the geotropic orientation which fol- 
low the cutting of the auditory nerve have thus far contin- 
ued for a month. 
These observations, it seems to me, prove that the geo- 
tropic phenomena observed in the shark are dependent upon 
the inner ear, and support the assumption of Breuer and 
Mach that they are called forth by the otoliths. 
But we can determine how the inner ear forces an ani- 
mal to maintain a certain position with reference to the 
horizontal as little as the botanists can explain how geotropic 
curvatures are called forth in plants. We can only say, in 
harmony with Goltz,' or Mach and Breuer, that the animal 
comes to rest only under a certain arrangement of strain and 
pressure in the peripheral ends of both auditory nerves. 
This arrangement exists in the shark when the animal turns 
1GoLTz, Pflugers Archiv, Vol. II. 
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