66 Records of the Indian Museum. [Vol. XXIV, 



I have myself examined specimens of the same species in our 

 collection and agree with Zugmayer's statement. Both Kessler 

 and Zugmayer believe that there is only one bladder in Dip- 

 lophysa and that the anterior part is enclosed in bone while the 

 posterior lies free in the abdominal cavity. Zugmayer found the 

 two bladders to be quite distinct from each other but regarded 

 them as parts of the same bladder. On examining the bladder in 

 young specimens of a new species from Eastern Tibet (Rham-tso) 

 I find that the two bladders are totally distinct from each other 

 and that they are not the two parts of a single structure. The 

 posterior bladder, that lies free in the abdominal cavity, is con- 

 nected with the oesophagus by a short pneumatic duct given off 

 from its anterior end. This duct is only distinct in young speci- 

 mens and atrophies in the adult. In order to understand the 

 true significance of the posterior bladder and its relation to the 

 anterior, it is necessary to examine the various types of bladder 

 commonly met with among the different genera of Cyprinoi- 

 dea. 



The swim-bladder of a typical Cyprinid fish such as Labeo 

 rohita is large and lies free in the abdominal cavity. It is con- 

 stricted in the middle to form an anterior and a posterior chamber 

 (fig. la). The pneumatic duct from the oesophagus opens into the 

 constricted region. In those genera that live in rapid running 

 waters the bladder undergoes considerable degeneration ; this 

 consists firstly in the gradual reduction of the two chambers and 

 the ultimate disappearance of the posterior, and secondly, in the 

 thickening of their walls. In extreme cases the bladder becomes 

 completely enclosed in a bony capsule derived from the transverse 

 processes of the adjacent vertebrae. 



In the genus Psilorhynchus the posterior chamber is greatly 

 reduced and the anterior is covered by a thick fibrous coat (figs. lb, 

 ic). In Nemachilus vittatus from the Kashmir Valley the anterior 

 chamber is laterally flattened and covered by a bony capsule while 

 the posterior chamber is small and thick walled (fig. if). The 

 pneumatic duct still opens into the constricted region between the 

 two chambers. In other species of this genus the anterior part is 

 divided into two lateral chambers which are enclosed in a bony 

 capsule and all remains of the posterior chamber are wanting. 

 In A diposia rhadinaea there is still a short bulb-like structure re- 

 presenting the posterior chamber (fig. ig) otherwise it is very 

 similar to that found in most species of Nemachilus. In extreme 

 cases such as Balitora brucei the two lateral halves of the anterior 

 chamber are much reduced and are somewhat separated from 

 each other (fig. ih). 



Among the members of the genus Diplophysa the anterior 

 bladder (fig. ij), which is enclosed in a boivy capsule, is in all 

 probability similar to that found in the genus Nemachilus and, 

 thus, it may represent the primary or the true original bladder of 

 the fish. The posterior bladder, that lies free in the abdominal 

 cavity, is a secondary structure and in its origin and position is 



