SEA-EISHERIES LABORATORY. 261 



into the epidermis. The nerve supply to the otocyst is 

 derived from the oesophageal connectives. Around the 

 point of origin of this nerve and along its course are 

 numerous large ganglion cells with vesicular nuclei. The 

 nerve comes into contact with the otocyst at the point 

 where the tube leads off to the exterior and is intimately 

 related to both structures as it provides them with a 

 sheath of nervous elements. The nervous sheath lies 

 below the epithelium of the otocyst and tube, among the 

 nerve fibres occur scattered fusiform or stellate cells. 



The otocyst, in life, contains a fluid of a somewhat 

 viscous nature which consists of a secretion of the walls 

 of the otocyst and its tube mixed with sea water. It also 

 contains numerous otoliths in the form of foreign bodies 

 such as quartz grains, portions of spicules, frustules of 

 diatoms, &c. In some specimens the original otoliths, 

 which were irregular in shape, have been covered by layer 

 upon layer of secreted substance of chitinoid nature, the 

 resultant otoliths having rounded outlines. This condi- 

 tion is met with in moderately old specimens (130 to 250 

 mm. long) in which also the tube of the otocyst has 

 become closed either by apposition of its walls or by the 

 blocking of the lumen by a granular substance secreted by 

 the gland cells in the wall of the tube (fig. 50). That 

 this rounded character of the otoliths depends upon the 

 closure of the tube is shown by the fact that in other 

 specimens (about 170 mm. long), in which the lumen of 

 the tube is a fair-sized slit, the otoliths are irregular and 

 uncoated foreign bodies. In most young specimens the 

 otoliths consist of irregular bodies which are almost naked, 

 i.e., they have either no secreted covering or else it is a 

 mere film the presence of which is indicated by its staining 

 with heematoxylin. 



Whenever the otocvst is examined fresh under the 



