152 DYNAMICS OF LIVING MATTER 



gravitation, when the otoliths were of iron. If, e.g., the magnet were 

 approached from the right side of the animal, the iron otolith would be 

 pulled toward the right, and this should result in a reflex turning of the 

 animal upon its left side. Kreidl found indeed that this occurred.* 

 Kreidl's experiments were repeated and confirmed by Prentiss. 



Delage, Kreidl, and Lyon all agree that the "maintenance of equi- 

 librium " or more correctly speaking the geotropic reactions of the 

 animal do not entirely disappear when the small antennae are cut off. 

 This proves that another organ contributes to these reactions, namely, 

 the eyes. Removal of the eyes and the antennae does away with the 

 compensatory motions. 



While it is thus probable that the otoliths have something to do 

 with the reactions of the animal, it does not seem as if this were gen- 

 erally the case. The flounder possesses a single large otolith in each 

 ear, which can easily be extracted without injury to the ear. Lyon 

 found that if the otoliths were removed, the geotropic reactions and 

 "maintenance of equilibrium" were not disturbed. 



This field requires further investigation, and I should not be sur- 

 prised if it were found that the really geotropic reactions of animals 

 were determined in certain cells of the inner ear, or in certain cells of 

 the brain, while otoliths may or may not act in an accessory way. It 

 would, however, be a mere anthropomorphism to assume otolith organs 

 inside the cells (as some botanists now begin to do for plants). Inside 

 of the cells of geotropically sensitive organs gravitation may probably 

 act through an influence upon the reaction velocity of certain chemical 

 processes, as set forth at the beginning of this chapter. 



4. CHEMOTROPISM AND RELATED PHENOMENA 



Theoretically we may assume that if substances diffuse in air 

 or in water, the particles move in a straight line away from the center 

 of diffusion. If they strike an organism whose surface is affected 

 by the diffusing substances on one side only, the contractile proto- 

 plasm, or the muscles, turning the tip or the head or the whole organ- 

 ism toward that side, are thrown into a different state of contraction 

 from their antagonists. The consequence is a turning or bending 

 of the tip or the head until symmetrical points of the chemically sen- 

 sitive surface of the body are struck by the lines of diffusion (or the 

 diffusing particles) at the same angle. As soon as this occurs the con- 

 tractile elements on both sides of the organ, or organism, are in an equal 



* Kreidl, Sitzungsber. der Wiener Akademie der Wissensch., Vol. IO2, Abth. 3, p. 149, 

 1893- 



