VII 



POSITION AND FORMATION OF THE OTOCYSTS 



197 



of the body and are rarely connected with it by any passage or 

 tube ; it is probable therefore that sound reaches them simply 

 through the medium of the tissues. 



In the Pelecypoda the otocyst is similarly situated near the 













--''C2 





'^% 





Fig. 96. — Illustratiug the otocyst in A, Anodonta, B, Cyclas; ot, otolith; a, h, c, c', 

 cellular layers surrounding the chamber; ci, cilia on interior walls of chamber: 

 C, an otolith crushed. (After Simroth.) 



pedal ganglion, and is probably (though this has not yet been 

 proved) similarly connected with the cerebral. There is only a 

 single otolith. Pelseneer finds ^ in Nuculidae alone a free com- 

 munication between the otocyst and the exterior. Aiiodonta has 

 been observed ^ to withdraw its foot into the shell at the noise 

 of an opening door, a loud voice, or a shrill whistle, whether in 

 a basin of water or lying on a study table. 



Delage extirpated the otocysts in certain Octopoda, and 

 obtained some unexpected results. He found that remarkable 

 effects were produced upon the animal's powers of locomotion, 

 so that it was unable to preserve its proper balance in the water 

 when in rapid motion, but its body was forced to undergo a 

 form of rotation more or less pronounced. He concluded that 

 the otocysts must possess, besides their auditory functions, a 

 power which stands in some relation to the proper orientation 

 of the body in locomotion, a power which is not wholly supplied 

 by sight and touch alone. The otocysts may thus regulate loco- 

 motion by stimulating muscular acts which tend to keep the 

 body in the straight line during the process of movement.^ 



1 Zool. Jahrb. Anat. iv. (1890) p. 501. 2 Baudon, Rev. Mag. Zool. 1852, p. 575. 

 ^ Arch. Zool. Exp. Gen. (2) v. 1887, p. 2 ; compare also C. H. Hurst, Natural 

 Science., ii. pp. 350, 421. 



