PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA, 231 



position in swimming resulted in twenty-one trials out of the twenty-five 

 made. The animals turn over and over, rotating about the long axis, 

 now in one direction, now in the other ; they also pitch forward and 

 backward about their transverse horizontal axis, and often swim upon 

 their backs. They do not resist overturning, unless holding to some 

 stationary object, and make no attempt to right themselves when swim- 

 ming free. The moment they come in contact with a horizontal sur- 

 face, such as the bottom of an aquarium, they at once take up their 

 normal position, righting themselves quickly, but if the surface they 

 touch be oblique or vertical, and even if they come in contact with 

 the under side of a horizontal surface, they cling to it tenaciously, 

 taking up a position with reference to the plane of contact, and not in 

 relation to the dii-ection of gravity, as is the case with normal ani- 

 mals. Thus the phenomena of orientation completely disappear in 

 the majority of cases when both otocysts and eyes are rendered func- 

 tionless, at least in the free-swimming animal. When the animal 

 comes in contact with solid objects, the sense of touch asserts itself 

 and the phenomena of orientation are again, to a certain degi'ee, made 

 manifest. 



d. One Eye blinded^ both Otocysts removed. The conditions here 

 are essentially the same as when only the otocysts are extirpated. 

 There is a well-defined rolling motion in swimming, and if overturned 

 artificially, the animal is very slow in regaining the original position. 



e. Both Eyes blinded, one Otocyst removed. In such experiments 

 no effect was produced different from that brought about by blindinc' 

 alone. There was no evidence of a tilting of the dorso-ventral axis 

 toward the injured side, as might be expected, if the functions of the 

 two otocysts were co-ordinated. Nor was there during swimmino- 

 a rotation toward the side from which the otocyst had been re- 

 moved. We may therefore conclude that in the phenomena of equi- 

 libration each otocyst, as well as each eye, acts independentlv. 



As check experiments, both antennules were removed distal to the 

 otocysts. No abnormal conditions were produced in swimming move- 

 ments, the wounds healed, and these individuals lived in aquaria as 

 long as normal animals. Where the otocysts were extirpated, individ- 

 uals were kept as long as four weeks, and after this interval, when 

 blinded, they gave the same evidences of loss of orientation as they did 

 immediately after the operation. 



These observations, made upon Palsemonetes, were found to hold true 

 also for Crangon, Mysis, and lobster larvae. Experimentation with the 



