158 



ZOOLOGY. 



utter a more distinctly musical sound than any other of 

 those observed by Abbot, who states that "it is a single 

 note, frequently repeated, and has a slightly metallic reso- 

 nance." It should also be noticed that the organs of hear- 

 ing in many musical fishes are said to be unusually well 

 developed, hence these sounds are probably love-notes; and 

 Abbot notices the fact that these fishes are dull-colored 

 during tiie reproductive season, as well as at other times, 

 while voiceless fishes, such as tlie percli, common sun fish, 

 chub, roach, etc., are highly colored during the breeding 





Mr >**-» ti*"*? , J. 



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Fig. 203.— Gizzard Shad. 



season, and thus the sexes are mutually attracted in the 

 one case by music, and in the other by bright colors. 

 Finally, tlie sounds of fishes may be compared with those 

 of reptiles, birds and mammals, the air-bladder correspond- 

 ing to the lungs of the liigher Vertebrates, while the pneu- 

 matic duct is comparable with the trachea of birds and 

 mammals. 



In swimming, the propelling motion is mainly exerted 

 by the tail, the movements of which are somewhat like 

 those of an oar in sculling. The spines of the tail-fin are 

 movable, and are capable of being brought into such a 

 position that the fin will meet with less resistance from the 



