GAR-PIKES, OLD A.VD TO DWG. 



its Jaws widely and apparently gulped in a large volume of air, 

 then descended and remained quiet for the usual interval. 



It 



FiQ. 5 View from below of the TJppeb or Dorsal Wall op the Throat of the Long- 

 nosed Gar {Lepidosteus osseus). One-half Natural Diameter. 



The oesophai^us is removed exceptinsf that part of the dorsal wall (.4/) which is closely attached to 

 the air-bladder (.4). Its cut edges are indicated by x x. Ch is the opeuinij or ' chiuli " lead- 

 ing into the air-bladder, and V Cindicate projecting points at the sides of the chink. HP, hy- 

 popharyngeal bones armed with teeth. 



The escaping air should be chemically examined. But, so far as 

 the experiments go, it seems probable that, with both Amia and 

 Lepldosteus, there occurs an inhalation as well as exhalation of air at 

 pretty regular intervals, the whole process resembling that of the 

 Menohranchus and other salamanders, and the tadpoles, which, as the 

 gills shrink and the lungs increase, come more frequently to the sur- 

 face for air. 



But the reader may say : " These fishes have gills, of course ; but 

 have they also lungs ? " To this the answer is both yes and no ; for 

 there are at least two different ways of interpreting certain facts ; 

 and some definitions are not as yet wholly agreed upon. 



Fig. 6. Cross-Section of the Air-Bladder of L osseus. One-half Natural Diameter. 

 The central open space is the median channel; on each side is seen one of the numerous sabdi- 

 visions of the lateral portions of the air-bladder. Above are the median aorta and the two 

 lateral veins, as in fig. 3. 



The facts are as follows : the Lepidostens and Amia, like many 

 other fishes, have an air-bladder a sac lying under the spine and 

 above the alimentary canal, and communicating by a slit-like orifice 

 with the upper side of the throat. With sturgeons and catfishes and 

 most common fishes, the sac is nearly or quite simple, and the com- 

 munication with the throat may be very narrow or even closed Such 

 fishes are not known to swallow air, and there is need of further infor- 

 mation as to the composition and source of the contained gas. But 

 the air-bladder of A>>u'a 2A\^ Lepidosteus is divided into many cells, 



