26 F. W. GAMBLE AND J. H. ASHWORTH. 



short nerve from the oesophageal commissure supplies the 

 otocyst. 



If the otocyst of a fresh shore lugworm be rapidly dissected 

 out under sea water and mounted^ the sand-grains will be seen 

 to execute a most extraordinary movement. Each one is 

 rotating slowly and jostling its fellows, so that the whole 

 contents of the flask are in a state of commotion. The fluid 

 in which the otoliths move is slightly viscous^ and is a secretion 

 of the walls of the otocyst, mixed with a little sea water. The 

 sand-grains are covered with a distinct layer of some chitinoid 

 substance soluble in boiling potash. Acids have no appreciable 

 effect upon these grains, and under the polariscope they react 

 as quartz does. Hence it seems clear that the otoliths of 

 Arenicola marina (the other species of the genus diff'er 

 most remarkably in this respect, as well as amongst them- 

 selves) are quartz grains covered by an organic film, and sur- 

 rounded by a fluid which is not merely sea water. 



Large specimens of the "Laminarian^^ variety were examined 

 without being opened under sea water, and the otocysts were 

 mounted by us in coelomic fluid. No movement of the oto- 

 liths was observed even in specimens which were perfectly 

 healthy in all respects. The otoliths sometimes filled the 

 expanded part of the organ, and it is possible that they had no 

 room to turn round. But it appears to us more likely that if 

 we assume the cause of the rotation to be the difi'usion caused 

 by liquids so difi'erent as sea water, in which the preparation 

 was first mounted, and the somewhat viscous, perhaps albu- 

 minous fluid inside the otocyst ; then if we mount the otocysts 

 in the same kind of fluid which they contain, no movement 

 should occur; and the experiment showed that in these cases 

 no movement did occur. The whole matter is one of very great 

 interest, especially in view of the probable functions of such an 

 organ as the otocyst. Ehlers has suggested that the movement 

 is due to the cilia at the bottom of the neck of the otocyst ; 

 but the same extraordinary movements are seen in the otocyst 

 of A. Grubii, which is closed and has no cilia. We quite 

 agree with Ehlers that there are no cilia in the expanded part 



