FISH IN GENERAL. 79 



shape of mushrooms standing on pedicles ; several congers 

 have the posterior opening under the lip. According as the 

 cavity is round or lengthened, the pituitary membrane is 

 folded in radii from the centre, or plaited on the two sides of 

 an axis in regular pectinations, like the barbs of a feather, 

 which in some cases, as in sturgeon, are farther subdivided in 

 smaller branches ; upon their surface are numerous ramifica- 

 tions of minute vessels, and upon them there is a mucous 

 fluid : the olfactory nerve, issuing from the anterior tubercles 

 of the brain, is single, double, or in several threads. In some 

 it swells into a ganglion on reaching the nasal cavity ; in all 

 cases its fibres traverse all the folds of the pituitary membrane 

 with great regularity. It may be conjectured that the number 

 and extent of their folds indicate the degree and power of 

 this organ of smell in the species ; but this power is still only 

 comparative. Finally, it is not impossible that the delicate 

 pituitary membrane gives also the faculty of distinguishing 

 the substances impregnating water, not odorous in themselves, 

 but of a nature to be avoided by the fish. 



The organs of taste appear to be weak in animals who 

 almost invariably swallow their food without mastication. 

 Even those whose jaws are provided with teeth, fit to cut and 

 bruise their aliment, cannot keep it long in the mouth, on 

 account of the position and play of their respiratory organs; 

 no salivary glands lubricate the parts with a moisture proper 

 to enliven the sense of tasting, and those parts are in them- 

 selves sufficiently insignificant. There are species which 

 have not even a prominence in the mouth that can be called a 

 tongue : no fish have one provided with muscles proper for 

 extending or inflecting it as in mammalia. Where the tongue 

 is the most fleshy in appearance, it is composed of cellulous 

 and membranous matter, fixed on the anterior part of the 

 lingual bones : the surface is commonly furnished with teeth, 

 sometimes so closely disposed as to form a kind of pavement, 



