1922.] Swim-bladder in Hill-stream fishes. a 
reduced as the bladder. _ It is possible, gence that a bony 
capsule is developed round the bladder © provide it with a 
protection so that it may be able to carry on the function, 
which it performs in correlation with the ear. Or p erhaps 
according to the neo-lamarckian school, the reduced binddes 
caused some irritation on the adjacent bones and er gad 
a capsule of bone was developed. At present, however, no- 
thing can definitely be said on this point. The reason for 
the reduction of the bladder is quite apparent, for in fishes 
that live in rapid pepe a balloon-like structure is of great 
disadvantage. hat animals living in mountain torrents 
require is solidity aa not bouyancy. 
Si ge Os ln Beas A an ae de ey a A ae 
