TOWER, PRODUCTION OF SOUND IN CERTAIN FISHES 155 



Dufoss6 (1874) in his memoir on "Sons Expressifs Produits par les 

 Poissons d 'Europe" has given an accurate and complete anatomical de- 

 scription of the air-bladders of the European Zeus faber, Dactylopterus 

 volitans and various Triglidne. Inasmuch as the air-bladders of the Trig- 

 lidse of the North American waters differ in some respects from those de- 

 scribed by Dufosse, I will here state briefly the structure in the species 

 under examination, Prionotus carolinus, or the red-winged sea-robin, as 

 well as of Opsamis tan, or the common toad-fish. 



Sea-robin {Prionotus carolinus).— The air bladder of Prionotus (Fig. 3) 



A B 



Fig. 3. SwiM-BLADDER OF PrIONOTUS CAROLINUS. 



A, Viewed externally, i m, intrinsic muscle; c I, connecting lumen. 



B. Longitudinally bisected, r, right lobe; g, internal septum; c o, central open- 



ing of septimi. 



is a deeply bi-lobed organ, occupying about two-thirds the space of the 

 abdominal cavity. The two lobes are connected near the anterior end by 

 a rather small tube. Along the outside portions of the respective lobes is 

 found a muscle, red in color, and running from the anterior end of the lobe 

 to the posterior end. The muscles adhere strongly to the underlying coat 

 of the air-bladder, and can be separated from it only with difficulty. The 

 muscle-fibres run in the plane of the short axis of the bladder. These 

 muscles correspond to the "intrinsic muscles" of Dufosse. The bladder 



