PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. Dol 
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 direction 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 degree, 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 blinding 
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 swimming 
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 independently. 
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 Palezemonetes, were found to hold true 
also for Crangon, Mysis, and lobster larve. Experimentation with the 
