POSITION AND FORMATION OF THE OTOCYSTS 



197 



of the liody and are rarely connected with it ])j any passage or 

 tube ; it is probable therefore that sound reaches them simply 

 through the medium of the tissues. 



In the Pdecyiioda the otocyst is similarly situated near the 



Fig. 96. — Illustrating the otocyst in A, Anodonta, B, Cyckts ; ot, otolith; a, 0, c, c', 

 cellular laj'ers snrrouudiiig the chamber ; ci, cilia on interior walls of chamber : 

 C, an otolith crushed. (After Simroth.) 



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

 proved) similarly connected with the cerel)ral. There is only a 

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

 munication between tlie otocyst and the exterior. Anodonta 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 extu^pated the otocysts in certain Octopoda, and 

 oljtained some unexpected results. He found that remarkaljle 

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

 that it was unal)le 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. Tlie otocysts may thus regulate locomo- 

 tion by stimulating muscular acts which tend to keep the body 

 in the straight line during the process of movement.^ 



' Zool. Jahrb. Anat. iv. (1890) p. 501. - Baudon, Rev. Mag. Zool. 18.52, p. 575. 



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

 Science, ii. pp. 350, 421. 



