242 Journal of Comparative Neurology. 



much force. In one case equilibrium lost by destruction of the 

 otolith was regained, after two days, by means of (or at least 

 coincident with) the regeneration of the stone. More observa- 

 tions of this kind would have strengthened his position greatly. 



As to the mechanism by which the equilibrium position is 

 assumed, " It is easily intelligible " says Verworn, "that the 

 varying pull and pressure which the otolith exerts upon the 

 hairs between whose ends it is suspended, must call forth a 

 varying stimulation in the hairs, which expresses itself in a 

 stronger or weaker activity of the cilia or in a total cessation of 

 the same." Being unable to prove any response to sound on 

 the part of Ctenophors, Verworn believes the otolith to be 

 solely a geotropic organ and proposes the names "statolith " 

 and "statocyst, " in place of otolith and otocyst, as terms which 

 recognize what he considers the true function of the organs. 



III. Weitere Beitrage ziir Physiologie der Olwlabyjinthes, 

 A. Kreidl, 1893, Sitzmigsbctichte der K. Akad. d. Wiss., 

 Wien., V. 102, P. 149, 



Kreidl worked upon PalcBmon, the same crustacean that 

 Delage had used. At each moulting these animals, like the 

 crayfish and many other crustaceans, cast off the otoliths to- 

 gether with inner lining of the otocyst. Afterwards, by means 

 of their chelae, they place fine grains of sand or other hard par- 

 ticles within the cyst to act as otoliths. Kreidl placed Pal(Uinon 

 immediately after moulting upon finely powdered iron, and the 

 animals placed this in their otocysts. If an electro-magnet was 

 brought near, the iron otoliths were attracted and the animal 

 responded to the magnet in the same manner as to the force of 

 gravity. Suppose the magnet were placed at the animal's right 

 side, the crustacean "would have the sensation" of being in- 

 clined to the right and would turn so that its sagittal plane lay 

 in the line of the resultant of the forces of gravity and the 

 magnet, just as this plane was in the vertical when gravity 

 was the only active force. This experiment of Kreidl's is 

 perhaps the most satisfactory as well as the most ingenious 

 that has been performed. It surely seems that the orientation 

 of the animals with respect to gravitation is effected through 



