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Tone Perception in Gammarus pulex. 

 By F. J. Cole, B.Sc, Professor of Zoology, University College, Reading, 



(Communicated by A. E. Shipley, M.A., F.R.S. Received January 17, — 

 Read April 21, 1910.) 



The proof of the existence of a restricted tonal sense in any animal would 

 be of great interest. The present paper offers evidence of the occurrence 

 of this phenomenon in the Gamrnarids. Though it must be admitted that 

 the number of animals which responded to the tests was small, the response, 

 when it occurred, was so definite and unmistakable that a description of the 

 results seems desirable. My attention was first directed to the matter by 

 Miss Margaret Cussans, who was engaged at the time in working out, at my 

 suggestion, the circulation of Gammarus pulex on the living animal under 

 the microscope. We then noticed that this species responded only to the bass 

 note of the College chime, which, giving on examination 240 vibrations per 

 second, therefore corresponded to the B below middle C of the pianoforte. 



In the first place it must be noted that the animal responds (in water) 

 only when imprisoned in the compressorium or live box. This makes the 

 case the more interesting, since if the reaction had not been observed by the 

 merest accident, the same experiments might have been conducted on the 

 animals in their natural surroundings with absolutely negative results. They 

 are compressed only so much as to prevent wandering, whilst leaving their 

 appendages quite free. They may then be kept under observation on the 

 stage of the microscope. I had a special live box constructed so as to permit 

 a gentle stream of water being passed continuously through it. This prevents 

 asphyxiation, and allows a single specimen to be experimented with for a 

 longer period than would otherwise be possible. It is, of course, inevitable- 

 that the vibrations should be conveyed to the animal by the medium in 

 which it finds itself, and in this sense it is impossible to postulate true 

 audition (as usually understood) in any true aquatic species. The factor to 

 eliminate here is clearly the specific period of the medium itself, the energetic 

 vibration of which, in response to its own note, may vitiate the result of the 

 experiment. For this reason I used three types of live box and microscope, 

 without, however, any difference in the results being noticed. Further, the 

 fact that the response is only evoked by a limited range of tone, and then 

 witliout reference to any specific forced or sympathetic vibration of the 

 surrounding medium, intimates that the stimulus is associated with a 

 definite physiological status of the animal itself, since even if the box were 



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