198 ME. I". DAT ON AMPHIBIOUS AND 



On Amphibious and Migratory Pishes of Asia. 

 By Tbancis Day, Esq., E.L.S. 



[Eead January 18, 1877.] 



Neablt nine years since (May 14th, 1868) I laid before the Zoo- 

 logical Society of London the results of some investigations which 

 I had made in Madras respecting the modes of respiration 

 amongst Indian freshwater fishes. Since that time, although 

 more facts have come to my notice, materials have scarcely been 

 sufficient to enable me positively to prove the amphibious nature 

 of some of these inhabitants of the waters of the plains of 

 Asia. 



Now, however, mainly due to the assistance I have received 

 from several friends, more especially Dr. Hubrecht of Leyden, 

 I think that the period has arrived when I may venture again to 

 request attention to the facts which I have collected, in the hope 

 that comparative anatomists who have sufficient leisure will more 

 fully investigate the anatomical details. 



The existence of fishes in Tropical Asia having amphibious 

 manners has long been known ; but that they are amphibious, in 

 the true sense of the word, appears to be doubted by a portion, at 

 least, of the scientific world. Professor Huxley has remarked 

 " that there are some fishes which, besides gills, possess an appa- 

 ratus for breathing air directly. This apparatus, represented by 

 the air-bladder of ordinary fishes, first takes on its new character 

 and becomes a lung in that remarkable genus Geratodus, in which 

 it exists as a large cellular structure situated in the upper part 

 of the abdominal cavity just under the vertebral column, and 

 connected with the gullet by a slit (the glottis), by means of 

 which the fish can pass air from the mouth into the lungs. It is 

 not, however, this peculiarity of opening into the oesophagus 

 which constitutes a lung ; for the air-bladder of many fishes pos- 

 sesses an open duct of a similar nature : the great distinguishing 

 feature is, that the blood taken to this bladder does not pass into 

 the ordinary venous channels, but is returned immediately to 

 the heart in a purified condition by a special vein." (' Nature,' 

 March 23, 1876, p. 411.) 



The above extract would appear to advance the three following 

 propositions : — 



First. That in fishes we first perceive the swim-bladder assum- 



