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THE AMERICAN NATURALIST. [Vol. XXXVIII. 



end of the aquarium, the fishes almost always responded by one 

 of a number of reactions. The most important of these were : 

 a rapid vibration of the tail without locomotion ; sudden jerks of 

 the tail frorfi side to side, often so vigorous as to cause a swift 

 dart forward ; normal locomotion, forw^ard, backward, or to one 

 side ; or in those fishes which lay at rest with the pectoral fins 

 folded, a vigorous spreading of the pectorals. It was evident 

 that individual goldfishes differed from one another in their 

 reactions much more than the individuals of Fundulus as 

 recorded by Pa'rker (: 03", p. 5 i). When a fish was tested with 

 the vibrating fork, it might respond by any one of these reac- 

 tions, but every fish had one distinct reaction characteristic of 

 it, which the application of the fork rarely failed to elicit. 

 Thus, the more active fishes usually responded by vigorous 

 locomotion, the more quiescent ones, by tail or fin movements. 

 Although fishes on which no operation had been performed, 

 usually responded to the sound, one, an albino, and a very 

 sluggish individual, gave no response. The fact that this one 

 died soon after my observations on it were made, is perhaps an 

 explanation of its unusual condition. As an example of the 

 characters of the responses, the following record of ten tests 

 from my laboratory note-book may serve. This record relates 

 to a fish which was subsequently operated upon by cutting the 

 eighth nerves. 



1 . Tail-jerks, followed by forward swimming. 



2. Tail-jerks, then forward swimming after an interval of 

 half a second. 



3. Sudden tail- and trunk-jerks, followed by forward swim- 

 ming. 



4- Tail-jerks, but without locomotion. 



5. Tail-vibration, but without locomotion. 



6. Strong tail-vibration followed by a turn to one side. 



7- Tail- and trunk-jerks, followed by forward swimming. 

 8. Tail-vibration, followed by a sudden turn to one side. 

 9- Tail- and trunk-jerks, followed by a turn to one side. 

 10. Tail-jerks, and sudden iumi forward. 

 In all, I made 193 tests on 18 normal fishes, and observed 

 150 responses, about 78 of the w^hole. Of the 43 failures, to 



