774 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [2Sj 



assume, as Hasse did, that we are dealing with a sound-conducting 

 channel or medium specially intended for the sacculus. At present I 

 cannot yet enter upon the details of the relations of the labyrinth to the 

 gill cavity in the Teleostei, to which I must refer to special descriptions 

 to be published later, upon the crania of separate families of osseous 

 fishes. 



ISTow that the grounds for the assumption have been demonstrated, 

 that in bony fishes the sound-waves for the most part reach the labyrinth 

 from the gill cavity, the remaining question presents itself as to how the 

 sound-waves get into the gill cavity. There can be no doubt that the gill 

 cleft plays an important part here ; still I believe I am able to point out 

 yet another chantHl which, according to physical principles, must be even 

 better suited for the purpose. I mean the conduit which is presented in 

 the bon es of the opercular apparatu s, especially by the operculum and sub- 

 operculum . If one reflects that these bones are thin elastic plates in most 

 Teleosteans, which through their broad surface are in contact with the 

 water contained in the gill cavity, and covered as they are by a thin 

 skin only, anct at no time being covered by large masses of soft parts 5 

 then one must admit that an apparatus, thoroughly suited to the pur- 

 pose, here presents itself for the conduction of the sound-waves from 

 the outer medium to the body of water in the gill cavity. Should fur- 

 ther investigations confirm this supposition, it would establish the state- 

 ment formerly made by Geoffroy St. Hilaire who, as we are aware, de- 

 clared that the opercular bones were ossicula auditus ; to be sure in 

 an entirely different sense from what this author meant. Although 

 somewhat foreign to the subject of my paper, a comparison of the sound- 

 conducting media of the bony fishes with those parts in other verte- 

 brated animals, especially the Selachii, is of great interest, because such 

 comparisons very well illustrate the position that the Teleosteans hold 

 with respect to other vertebrates. 



The common opinion is, that differentiated sound-conducting appa- 

 ratuses first made their appearances in the Amphibia, more particularly 

 among the Anura. It has already been sufficiently dwelt upon that 

 this view is an erroneous one, and that in the majority of bony fishes 

 no general conduction of the sound-waves to the labyrinth takes place; 

 that, on the contrary, channels have been differentiated of a constant 

 character. But osseous fishes are not the forms — in the vertebrate 

 series — in which such auxiliary apparatuses to the organ of hearing 

 first appear; contrivances for such purposes can already be demonstrated 

 to exist in the Selachians, from which the apparatuses in the bony fishes 

 were derived. The credit belongs to Johannes Miiller^" for being the 

 first to truly recognize and appreciate these conditions in the Selachians; 



*° Vergleichende Anatomic der Myxinoiden. Theillll. Das Gefiissystem der Myxinoiden,. 

 Abhandt. d. Berlin. AJcademie d. Wissenschaften von Jahre 1843. [Comparative Anatomy 

 of Myxinoids. Part III. The vascularsystem of the Mysinoids. Treat, of the Berlin 

 Academy of Sciences, 1843. ] 



