162 ANNALS NEW YORK ACADEMY OF SCIENCES 



existent reellement ils doivent pouvoir varier d'une certaine quantite sans que le 

 degre de renforcement des sons soit grandement modifi^." 



In speaking of the ScisenidEB, Dufosse says that the sound is produced 

 for the most part by muscles; but a little later, in speaking of Psevdo- 

 sciaena aquila, he says 



" Le mecanisme de la production des sons chez les iudividus de I'espece Scicena 

 aquila est plus compliqu^ que celui des poissons dont j'ai parl6 jusqu' k present 

 (lyre). Je n'ai nullement la pretention de donner la th^orie de ce mecanisme." 



Just why Dufosse makes this statement is not intelligible, for all the drum- 

 ming fishes of America that have been examined have the same mechanism, 

 and it is very evident that the sound is produced in exactly the same way. 

 As Dufosse examined only European forms, however, he may have ob- 

 served a difference in structure that is not present in the American species. 

 The fact that Dufosse stated that he could not explain the mechanism 

 in Sciosna, while for the Gurnard lyre his exj')lanation was not in accordance 

 Avith physical phenomenon, has possibly led more recent ichthyologists to 

 ignore his work. Thus we find that Giinther (1880) in speaking of the 

 A merican drum {Pogonias cromis) says, 



"It is still a matter of uncertainty by what means the "Drum" produces sounds. 

 Some naturalists believe that it is caused by the clapping together of the pharyngeal 

 teeth, which are very large molar teeth. However, if it be true that the sounds are 

 accompanied by a tremulous motion of the vessel, it seems more probable that they 

 are produced by the fishes beating their tails against the bottom of the vessel in 

 order to get rid of the parasites with which that part of their body is infested." 



That these explanations of Giinther are unwarranted will be seen from 

 experiments soon to be described. 



Sorensen (1895) disagrees with Dufosse s statement that it is the vibra- 

 tion of the muscles while contracted which produce the sound and that 

 the air-bladder only intensifies the sound. Sorensen considers the sound 

 as being produced by vibrations of the air in the air-bladder and of the 

 walls of the latter when set in motion by the muscles with the fascia of 

 which it is connected. 



Jordan and Evermann (1902) say that "most of the species make a 

 peculiar noise, variously called croaking, grunting, drumming, or snoring, 

 supposed to be produced by forcing air from the air-bladder into one of 

 the lateral horns." 



We have presented to us then, four distinct mechanisms in the Sciffi- 

 noids : 



1. Muscular tone; the vibrating muscle producing a sound which is 

 intensified by the air-bladder (Dufosse). 



