THETARPON 51 



It is hoped that the foregoing information will be of 

 value to you. I have saved the air bladder which will be 

 available for further examination." 



Many of the old families of fishes doubtless had lungs or 

 breathing organs of some character but the air-bladders of 

 most of the mature modern teleosts fail to disclose their ex- 

 istence. A layman, like myself, having only a superficial 

 knowledge of the principles of evolution, would assume that 

 this organ would have developed to greater efficiency in the 

 modern fishes. Instead it has degenerated. 



If the reader is interested in an explanation of why this 

 degeneration has taken place, he is referred to the paper of 

 Mr. Charles Morris, entitled "The Origin of Lungs; a Study 

 in Evolution", first published in the American Naturalist of 

 December 1892, and reproduced in Jordan's "A Guide to the 

 Study of Fishes", (Vol. 1, p. 98). 



The lung tissues in the air-bladder of the tarpon afford 

 further evidence of its antiquity and imply that it has lived 

 in waters so deficient in oxygen content that it was forced to 

 breathe atmospheric air or perish. In the course of time, na- 

 ture provided the fish with an accessory breathing apparatus 

 which it now retains and still employs. This accounts for the 

 ability of the fish to live in stagnant pools as well as for its 

 habit of coming to the surface for air even when it is in the 

 pure and oxygen charged waters of the open sea. 



It seems clear from this careful investigation conducted by 

 Dr. Hildebrand that the tarpon secures the oxygen it re- 

 quires not only from its gills but also through the cellular 

 lung-like tissues in the air-bladder. The latter organ func- 

 tions somewhat similarly to the lungs of the higher verte- 

 brates. It is a respiratory as well as a hj^drostatic organ. 



But why did not these lung tissues in the air-bladder of this 

 fish degenerate? Does not their present existence force one 

 to the conclusion that the tarpon habitually lives for at least 

 a portion of its life in poorly oxygenated waters I I leave the 

 solution of this question to tl^e Ichthyologists. 



