6 Journal of the Asiatic Society of Bengal. [N.S., XVIII, 
The various phases described above represent a conti- 
nuous series in which the posterior chamber is being gradually 
eliminated and the anterior greatly reduced and enclosed in 
a bony capsule. The members of the genus Diplophysa are 
very peculiar. They inhabit the deep waters of Central Asia 
and in that situation require a hydrostatic organ. They 
posses a fairly well-developed bladder free in the abdominal 
cavity and have in addition a typical bladder of the Nema- 
chilus type anteriorly. The free bladder has a pneumatic 
abdominal cavity. To derive a bladder of the Diplophysa 
type from that of one described for Botia hymenophysa is very 
chilus there is none. Assuming the close relationship between 
advanced members of Nemachilus, in which the anterior cham- 
ber has become divided up into two lateral chambers, and 
those of the genus Diplophysa, it appears to me quite probable 
that the anterior bladder of Diplophysa corresponds to that 
found in Nemachilus, while the posterior bladder is a totally 
new structure evolved for life in deep waters secondarily. 
Which of the two propositions is correct, is very difficult to 
judge 
Having described some of the types of bladders met with 
in hill-stream fishes, it remains to account for the modifica- 
tions enumerated above. The reduction of the bladder seems 
Ha 
