EAR OF THE SQUETEAGUE. I219 



experimental purposes the sacculus is scarcely accessible from the dorsal or lat- 

 eral aspects of the head, but it is so near the roof of the mouth that I determined 

 to approach it from that side. As already stated, it is separated from the mouth 

 by only a thin layer of bone and mucous membrane. It was not difficult to 

 hold the mouth of a squeteague open and, by means of long bone forceps, to 

 cut through this thin wall and thus gain access to the sacculus, but this opera- 

 tion was attended with so much loss of blood that it was finally abandoned. 



Since the lateral wall of the sacculus is essentially nonnervous, it occurred 

 to me that I might force the sagitta off the sensory patch on which it rested 

 and against the nonnervous lateral wall by driving a pin in an appropriate direc- 

 tion through the thin roof of the mouth. A little practice on the heads of 

 dead fishes showed that this could be accomplished wath comparative ease. The 

 pins used were long steel hat pins about 8 inches (20 cm.) in length. 

 These could be easily manipulated in the open mouth of the fish, and after they 

 had been forced into place against the sagittae they could be cut off short next 

 the roof of the mouth. Apparently they offered no obstacle to the breathing 

 and other mouth movements of the fish. Squeteagues that had thus been oper- 

 ated upon lived about as long as normal squeteagues do in confinement. Of 

 10 fishes in which it was attempted to pin off the otoliths in this manner, 7 sur- 

 vived for nearly a week and were used in the following experiments. The 3 

 others died during the experiments, and hence their records were omitted as 

 incomplete. In all 10 cases, final dissection showed that the otoliths had been 

 pinned against the nonnervous side of the sacculus as was intended. The tests 

 carried out on the 7 vigorous fishes gave very uniform results. 



Before the otoliths were pinned down, each squeteague was tested with 

 the blinders for equilibrium and in the wooden aquarium for responses to sound. 

 After pinning down the otoliths the fishes swam at first irregularly, but in ten 

 minutes at most they regained their equilibrium, and they retained this even 

 when the blinders were put on them. After the immediate effects of the opera- 

 tion of pinning down the otoliths had disappeared, the equilibrium of these 

 fishes was indistinguishable from that of normal fishes. The vigor of their 

 movements was likewise unimpaired by this operation. After it they were 

 about as difficult to catch with a hand net as before it. On testing them 

 with sound stimuli they were found to be only slightly responsive as compared 

 with their former condition. Thus a fish that before the pinning of the 

 sagittse had responded to every tap of the mallet on the wooden wall of the 

 aquarium, reacted to only 3 in 30 taps after the sagittae were anchored laterally. 

 This considerable reduction in reactiveness was also noticed in the other 6 fishes. 

 When, moreover, a squeteague with the otoliths pinned down was placed in the 

 aquarium with a normal fish and the wall of the aquarium was tapped, it was 

 quite easy to determine from the movements of the 2 fishes which was the 



