A DEGENERATE GLAND. — PRINCE. 219 



and their lateral processes expand as a roof or bony shield over 

 the anterior portion of the swim-bladder. Even the South 

 American species Hypophthalmus, so universally regarded by 

 anatomists as lacking the swim-bladder, has been proved by 

 Professor Ramsay Wright to be no exception, the rudimentary 

 swim-bladder being present, completely paired (really two 

 separated vesicles), and partly enclosed in the vertebral body 

 and the walls of the neural canals and in the ossified tunica 

 externa (No. 26, p. 116), while it has connection with the 

 auditory organ by a chain of ossicles much reduced, but as Dr. 

 Wright points out, " after precisely the same plan as in the 

 other Siluroids," (loc. cit. p. 108). On each side a so-called 

 malleus connects with a stapes, by an incus, with the lateral 

 wall of the atrium sinus imparis,^the bones named being modi- 

 fied portions respectively of the first, third and second vertebras. 

 The stone-loach (Cobitis) like its congeners generally (the 

 Acanthopsidge) exhibits a bony case on each side of the most 

 anterior vertebrae, in which the two globular chambers of the 

 swim-bladder are enclosed side by side.* The two protecting 

 bulla3 are expansions of the transverse processes of the second 

 and third vertebrfe, (Plate 20, fig. 5, bb.), and hide from view 

 the chain of three ossicles. The tropical American and African 

 Characinida3 have a swim-bladder divided into two parts 

 connecting by a chain of ossicles, with the auditory organs as in 

 the Carps and Siluroids. The Cyprinodonts, diminutive carp- 

 like fishes very abundant in Canada, have, however, no such 

 auditory connection by a series of ossicles, while one Central 

 American species, Rividus, has been found to be destitute of 

 the swim-bladder altogether. The carps (Cyprinidai) and the 

 pikes {Esocida'), and other families like the oceanic Halisauroidei, 

 possess a simple swim-bladder, often a two-chambered sac with 

 thin membranous walls, opening into the gullet by a tube, while 



*The swim-bladder in Heterobranchxis and Malapterurns exhibits the two rounded 

 sacs. (Plate IV, figs. 8, 9.). 



