366 ZOOLOGY. 



The anatomy of fishes has received attention from many investigators, 

 among whom are Olga Metschuilvoff, M. von Davidoff, and G. Swirski, 

 wlio liave treated of the shoulder and pelvic girdles iu wliole or part ; A. 

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

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

 on the sides of scojielids and other types ; Ad. von La Valette St. George, 

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

 the heart and contiguous parts iu Butirimis 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. Eabl Euckhard; 

 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 E. H. Traquair. 



OKIGIN OF 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 sciiie- 

 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 assumed 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 iu full iu the " Naturhistorisk 

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

 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 i)ortion 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, and the sound is pro- 

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

 tion to the rapidity of the vibrations of the springs," — the" springs" 

 being the transverse apoi^hyses of the vertebme. 



* Sorensen (W. ) On the Apparatus of Sound in some Soutli American Fishes. Ann. 

 MaQ.Xat. Hist, (5,) vol. iv, pp. 99-100. (From Compies Ecndus, May 19, 1879.) 



