200 BULLETIN OF THE BUREAU OF FISHERIES. 



invariably by an increase in their respiratory rate. This; continued to he true even 

 after the nerves to the lateral-line organs had been cut. and I therefore concluded 

 that the lateral-line organs were not essential to these responses. Since the pectoral 

 tin and the respiratory reactions disappeared in individuals whose eighth nerves had 

 been cut, but whose lateral-line organs were intact, it was evident that while in this 

 species these sounds were effective stimuli for the ear they were not so for the lateral- 

 line organs. 



Fwndul ' ax mujalis reacts in many respects like F. heteroclitus. Its movements, 

 however, are often more sudden and darting than in the other species. To vibrations 

 of the tuning fork the animals usually spread the tins and often gave a short dart 

 forward. This continued after the nerves to the lateral-line organs had been cut. 

 and ceased only with the cutting of the eighth nerve; hence I conclude that also in 

 /'. majalis sound is a stimulus for the ear but not for the lateral-line organs. 



Although I tested a considerable number of Stenotomus chrysopsnuA Mustelus 

 eanis, both in normal condition and with their lateral-line nerves cut, I was unable 

 to elicit from them any unquestionable reactions to the sound from the tuning fork. 

 This stimulus certainly did not act on the lateral-line organs of these two fishes, and 

 from the experiments on the two species of Fundulus, I conclude that there is no 

 reason to suppose that a sound of 100 vibrations per second is a stimulus for the 

 lateral-line organs, though it may be for the ear. 



Vibrations of low frequency . — When a slow but noiseless vibration was given to 

 the aquarium containing Funduhts heteroclitus, the lishes, as I have elsewhere stated 

 (Parker, 1903a, 1903b), were vigorously stimulated. The stimulus that affects them 

 seemed to proceed from a movement of the body of water in the aquarium as a whole, 

 for the most convenient way to produce this stimulus was to make the aquarium and 

 the supporting table vibrate slightly by drawing the aquarium a little to one side, 

 thus straining the table slightly, and then letting it go. The motion thus produced, 

 when written off on a moving surface, was found to consist of a series of vibrations 

 very close to six per second, and each time the aquarium was made to vibrate, about 

 forty such vibrations were accomplished before the apparatus came to rest again. 



I have nothing to add to my former statements (Parker, 1903a, p, 59; 1903b. 

 ]>. L99) about the reactions of Fundulus heteroclitus to this stimulus. When normal 

 individuals are Hist introduced into an aquarium they swim at once to the bottom, 

 and only after some time and numerous cautious attempts do they come to swim at 

 the surface. As I have already noted, any slight disturbance, such as a quick move- 

 ment of the observer or a slight jar given to the aquarium, is sufficient to cause them 

 to descend at once. If, by means invisible to the fishes, the slow vibration already 

 described is given to the. aquarium, they dart at once to the bottom and remain 

 there some time before returning to the surface. When the fish again begin to 

 swim upward toward the surface, their progress may at any moment be stopped by 

 causing the aquarium to vibrate, for they will again descend. Under no circum- 

 stances will the normal tishes rise and stay at the surface while the aquarium is in 

 vibration. These reactions are in my experience practically invariable. 



When individuals with the nerves to the lateral-line organs cut are subjected 

 to similar tests, the contrast with normal fishes is striking. Cut fishes will continue to 

 sport about near the surface, or even swim upward from below, while the aquarium 



