FISHES. 
5 
they could not sink, and make off. It is, however, 
a curious subject for inquiry.”^ 
The Diodon, as is well known, has the habit of 
inflating its body with air, and of floating help- 
lessly in this condition at the surface ; but in this 
case it appears that the air is not taken into the 
bladder, but into the huge stomach, filling the 
cavity of the abdomen. 
A Gold-fish, in a small fountain, in the 
grounds of a gentleman of my acquaintance, 
swam about for more than two months, with its 
belly upwards. It appeared perfectly healthy 
and lively. This change from the natural posi- 
tion of the fish was, probably, owing to an en- 
largement or defect in the air-bladder.” f 
In conformity with their structure, the sphere 
of activity of Fishes is the water. The Flying- 
fishes, and some of the Gurnards, are able to 
elevate themselves into the air, and to maintain 
their position there for a few seconds ; and some 
of the Frog-fishes and Eels can crawl upon the 
exposed mud or sand, during the hours that inter- 
vene between the ebb and flow of the tide ; but 
these exceptions scarcely break the universality of 
the law which confines Fishes to the water. 
There is, however, considerable diversity in the 
locality assigned to different species ; some in- 
habit fresh-waters only, some only the sea ; 
others are able to exist in both, either by pe- 
riodical migration, or at pleasure. Of fresh-water 
Fishes, some inhabit large rivers, others small 
streams ; rapid and sluggish waters have each 
charms for some : great inland lakes possess 
peculiar species, and some are found only in the 
* Jesse’s Scenes of Country Life, 353. f Ibid. 356. 
