SOUND AS A DIRECTING INFLUENCE IN MOVEMENTS OF FISHES. 



103 



The second class of fishes is well represented by the sea robins {Prionotm carolinus 

 and Prionoius strigatus). 



Table V.— Directive Responses of Prionotus carolinus and Prionotus strigatus to Sound. 



The grand total of occurrences in a possible 2,500 in the half of the tank nearer 

 sound was 1,401, or 56 per cent. 



As table v shows, >oung specimens of Prionotus carolinus and Prionotus strigatus 

 exhibited unmistakable tendencies to gather near the sound center. In each of the 

 five groups tested the total numbers of occurrences on the side of the^ sound center 

 were well above 250, the point of indifference. These species, therefore, afford a good 

 example of fishes that move toward a sounding body in contrast to the four species 

 mentioned as forming the first group. It is a matter of some interest to note that sea 

 robins make a grunting noise themselves, and it may be that they hold together in 

 schools by following this noise, in which case their movements toward a sound center 

 such as was used in these experiments would be entirely natural. 



The third class of fishes consist of those which move neither toward a sound center 

 nor away from it. This class includes fishes that are much disturbed by sounds, but 

 instead of being directed by these disturbances cease locomotion after a moment or so 

 of swimming and remain quiescent till the sounding has come to an end. The best 

 illustrations of this class are the killifishes, Fundulus heteroditus and Fundulus majalis. 

 After they had become accustomed to their surroundings they swam about freely near 

 the surface of the water but when the sounding began they went at once to the bottom 

 of the tank and remained quietly in seclusion in any nook or comer that they could 

 find till the sounding had ceased. The cunner, Tautogolabrus adspcrsus, probably also 

 belongs to this class, though when under the influence of sound it often moves about 

 and its distribution indicates at times some tendency to move toward the sound center. 



From all these records collectively it is quite clear that some fishes move away 

 from sound centers, others move toward them, and still others, though much disturbed 

 by sounds, move neither toward nor awayfrom the sources. Throughout these experi- 

 ments it was generally noticed that after the sounding ceased the fish very quickly 

 returned to a state of normal locomotion and equal distribution. This condition is 

 well illustrated by records taken from Stcnotomiis. Five of these fishes were placed in 

 the tank, and after they had become quiet their distribution was recorded in the usual 



