I2l6 BULLETIN OF THE BUREAU OF FISHERIES. 



Since the ear of the squeteague is really double, in that the saccular and 

 utricular organs are anatomically separate, and since these organs are large 

 and fairly accessible, it seemed reasonable to expect that experiments upon them 

 might be devised which would lead to a more definite knowledge as to the 

 localization of function in these parts. 



UTRICULAR ORGAN. 



After some practice on the heads of dead squeteagues it was found possi- 

 ble to destroy the utriculus and semicircular canals of live fishes by cutting 

 them with a long, narrow knife blade inserted through a small incision on 

 each side of the head, and yet to leave the sacculus and its appended parts 

 uninjured. This operation could be performed without serious bleeding and 

 without injury to the brain. The slight opening thus made through the skin 

 and subcutaneous parts closed of itself, and even after the death of the fish 

 it showed no tendency to gap open. It was expected that these operations 

 would be followed by a loss of equilibrium, but it was soon clear that the sque- 

 teague could still keep its upright position. Since this fish, like many others, 

 is in unstable equilibrium (Monoyer, 1866) when in its so-called resting posture, 

 I suspected that the retention of its upright position after the loss of the utricular 

 organ was dependent upon the eyes, and to eliminate the action of these sense 

 organs a set of blinders was devised. These were attached to the head of the 

 squeteague by means of a cord harness. A single loop of cord was tied snugly 

 round the body of the fish just posterior to the pelvic fins, and from the point 

 at which this loop crossed the dorsal line a cord was run over the median dorsal 

 line of the head to the large premaxillary teeth, where it was made fast. To 

 this median dorsal cord were attached two cloth flaps that could be turned 

 down over the eyes and held there by a cord, passed from one flap to the other 

 under the jaws. In this way the eyes could be covered without interfering with 

 the freedom of movement of the mouth and gills, for unless these parts are 

 entirely free the animal is extremely restive and may even lose its balance. 



Five sets of four fishes each were tested for the effects of destroying the 

 utriculus and the semicircular canals. Before operating upon the fishes each was 

 tried to see that it responded to sound vibrations and that it swam normally 

 with the eyes covered. In testing the reactions to sound, the fish was placed in 

 a large wooden tank of sea water, and after it had become quiet the side of the 

 tank was tapped once or twice with a mallet in such a way that the fish could 

 not see the movements. At each tap the fish almost invariably made a slight 

 spring forward. To test the relation of the eyes to equilibrium, the harness 

 was put on the fish and the eyes covered by the blinders. The majority of 

 fishes immediately swam away slowly, though in normal equilibrium, but a few 



