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ANNALS NEW YORK ACADEMY OF SCIENCES 



is not connected with the exterior by a pneumatic duct, Giinther (1880) 

 to the contrary notwithstanding, for the entire bladder has been removed 

 from the abdominal cavity without losing any of the contained gas, an 

 operation which would be impossible if there were any means of commu- 

 nication between it and the exterior. 



The air-bladder itself consists of three layers — an external, a middle 

 and an internal — together with the pair of muscles just described. The 

 outer and middle layers are composed of thick, compact tissue, containing 

 both elastic and non-elastic fibres. The inner membrane is a mucous 



im 



IrT/h 



A B 



Fig. 4. Swim-bladder of Opsanus tau. 



A. Viewed in situ, i m, intrinsic muscle. 



B. Viewed externally. 



tissue provided with numerous blood vessels. Lying in this tissue are 

 found also the blood glands or red-bodies which were described in the 

 bladders of the scitenoids. 



The left lobe (fig. 3 B) in all specimens of Prionotus is divided into two 

 parts by a partition formed of the internal tunic or membrane. In the 

 centre of this partition is a small opening, a little larger than the head of 

 a pin. The right lobe is never divided. This perforated partition was 

 present in all specimens examined of both sexes. The cmbryological 



