10 



K. MITSUKURI. 



Fi 0, 5 C" ' ' IC '" ei ' < '" ''" ttei ' '' ue I* ^ IIL ' to nsKgl't shifting of the glass-plates. T!ie 



6" ' ' loop indicates tlmt the mollusc on that elevation was above the iraber- level. 



and conceal themselves. 



The conditions given in Fig. 5, C was left intact for two days. 

 During the interval, not a single mollusc stirred. On the fifth day (from 

 the beginning of the experiment), water was again lowered to the level 

 of Fig. 5, B. with the hope that there might be some downward move- 

 ments of the molluscs. But none stirred, and although the whole was. 

 left untouched for four days more, no movement was visible. 



Under what conditions, then, the molluscs moved downwards, re- 

 mained as much of a mystery as ever. I was greatly puzzled. Atone 



