366 ZOOLOGY. 



The anatomy of fishes has received attention from many iavestigators, 

 among whom are Olga Metschuikofl", M. von Davidoft", and G. Swirski, 

 who have treated of the shoulder and pelvic girdles in whole or part ; A. 

 Cisow, who has studied the ear; G. Carlet, who has examined tlie scales; 

 and M. Ussow, who has sought to explain the function of the "eye-spots" 

 on the sides of scopelids and other types ; Ad. von La Yalette St. George, 

 who has elucidated the adipose fin, and J. E. V. Boas, who has dissected 

 the heart and contiguous parts in Butirinns and related fishes. 



Certain groups have also received special attention. Omitting all 

 reference to work on the Teleosts, Petromyzon has been anatomized by 

 E. Weidersheim and J. E. V. Boas; the Selachians have been investi- 

 gated by G. B. Ercolani, C.Hasse, S.M. Garman, and H. Rabl Ruckhard; 

 the osteology of Polyodon has been described by T. W. Bridge, and the 

 embryology of Lepidosteus by A. Agassiz. Fossil fishes have been 

 described by E. D. Cope, J. W. Davis, and R. H. Traquair. 



OEIGIN or SOUNDS PRODUCED BY FISHES.* 



Many fishes are known to emit sounds of various kinds, and among 

 those inhabiting the United States are the drum-fish and other scijB- 

 nids as well as the catfishes. As to the drum-fish a recent writer (Dr. 

 Giinther, " Introduction to the Study of Fishes," p. 427) has assujued that 

 "a tremulous motion" is communicated to vessels, and that the noise is 

 probably "produced by the fishes beating their tails against the bottom 

 of the vessel in order to get rid of parasites." This remarkable hypoth- 

 esis renders exact observations noteworthy. The subject has received 

 attention from several naturalists, and among them Mr. W. Sorensen, 

 who has communicated to the French Academy of Sciences an abstract 

 of a memoir which is to be published in full in the " Naturhistorisk 

 Tidsskrift," of Copenhagen. Mr. Sorensen's observations were made ou 

 South American Characinids and Silurids. "The sound is produced by 

 the action of the muscles which are inserted either directly in the swim- 

 ming-bladder or upon the transverse apophyses of the third vertebra. 

 In the Characini the elastic parts of the swimming-bladder are stretched 

 in the direction of their length by the contraction of the muscles, and 

 the vibration that results from this rhythmic movement is transmitted 

 to the air contained in the cavity of the swimming-bladder. In the 

 Siluroids the anterior jiortion of the swimming-bladder is drawn alter- 

 nately forward and backward by the contraction and relaxation of the 

 muscles. During these movements the air in passing across the incom- 

 plete transverse septa sets the latter in vibration, arid the sound is i>ro- 

 duced. The height, or rather the depth, of the sound is in direct proi)or- 

 tion to the raj^idity of the vibrations of the springs," — the" springs" 

 being the transverse apophyses of the vertebrae. 



* Sorensen (W.) On the Apparatnsof Sonnd in some Soutli American Fishes. Ann. 

 Maff.Nat. Hist., (5,) vol. iv, piJ. 99-100. (From Comjptcs licndus, May 19, 1879.) 



