ox THE ANATOMY OF FISHES. 
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the same lines as in the Siluridse abnormales. The series of Weberian ossicles is 
complete, including even an intercalarium ; the anterior chamber of the typically 
bilocular Cyprinoid air-bladder, as a rule, alone persists, although in a much reduced 
condition ; the posterior chamber, if present at all, is scarcely more than the barest 
rudiment ; and it is tbe anterior alone which is encapsuled by bone. Furthermore, 
such characteristic modifications of the air-bladder are, in these genera, undoubtedly 
associated with a purely ground habit of life. Nemachilus barhatula, the commonest 
of English Cobitidinse, is unquestionably a ground Fish, its general habit being to 
lurk under stones at the bottom of rapidly -flowing streams, or, if nearer the surface, 
to rest on floating weeds. The popular names “ Groundling” and “ Stone Loach” 
sufficiently indicate the habits of this Fish. Cohifis tcenia, a much rarer English 
species, is also a “ ground” Fish, but it is said to be partial to muddy bottoms. Of 
the East Indian genus Botia, Day* remarks that it “ can scarcely be said to be 
entirely a ground feeder, but seems intermediate in habit between the true Carp and 
the grovelling Loaches.” In the condition of its air-bladder Botia exhibits a similar 
gradation between the two types, for, while the anterior chamber is completely 
encapsuled by bone, the posterior chamber, though reduced in size, is still better 
developed than in Cohitis and Nemachilus. 
So close a parallelism in the condition of the air-bladder and the habits of its 
possessor in two families so well defined and distinct, both in general characters and 
the structure of the air-bladder and Weberian mechanism, as the Cyprinidse and 
Siluridm, can only be due to the operation of similar causes in both instances, and in 
our opinion is strongly confirmatory of the conclusions we have already arrived at in 
the case of the latter family. But although the modifications which the air-bladder 
undergoes in the abnormal forms of both families are substantially similar in principle 
and in result, and have no doubt been evolved in each case to bring the organism 
into harmony with practically similar external conditions, there are certain minor 
differences between the two as to the precise means employed. Encapsulation of the 
air-bladder in the Cyprinidae appears invariably to result from the actual ossifi- 
cation of the walls of the air-bladder itself, the modified transverse processes taking- 
little, if any, share in the process. This may possibly be explained by the fact that 
in these Cyprinidse with a normally-developed air-bladder, the transverse processes, 
though greatly developed in size and otherwise modified, are never so expanded or so 
closely moulded to the anterior and dorsal surfaces of the anterior chamber as is 
always the case in the normal Siluridae, and hence, instead of encapsulation being 
effected, as is generally the case in the latter, by a slight extension of a modification 
already existing, it has been brought about in the former by the actual ossification of 
the outer coat of the air-bladder itself. The completeness of encapsulation in the 
Cyprinidae we associate with the general integrity of the rest of the air-bladder and 
Weberian mechanism, for reasons previously urged in the case of certain Siluridae 
* ‘ Cotteswold Nat. Field Club,’ 1880, p. 10. 
2 .s 
MDCCCXCTIT. — n. 
