FISHES. 372 



anterior part is very voluminous. In the cyprins the kidneys arc en- 

 larged, particularly opposite the constriction of the natatory bladder. 

 The ureters, more or less long, according to their genera, end in a 

 dilatation, which supplies the place of a bladder, and whose external 

 orifice is placed immediately behind the anus and the orifice of the 

 organs of generation, which themselves open, sometimes within, some- 

 times on the border even of the anus, but always at its posterior part, 

 Avhich is the inverse of what is seen in quadrupeds. Sometimes, as 

 in the chondropterygians, the orifices of the ureters and those of 

 the vasa deferentia give a cloacum which is either common or at 

 least in the same opening. 



The skin of fishes is moistened by various humours prepared by 

 appropriate vessels opening externally at different points according 

 to the varieties of the genera. This generally is a mucus which it is 

 exceedingly difficult to dilute Avith water. 



]n the ray there is at first, on the inferior surface, a large vessel 

 which surrounds the snout, forming there angles and very regular 

 circular lines, and which pours its liquor on either side by three or 

 four branches, reflecting itself upwards to terminate in a great num- 

 ber of little apertures, and we see further on each side, at the exter- 

 nal angle of the branchiae, a sort of round and while bursa, into 

 which a considerable branch of the fifth pair of nerves penetrates, 

 and from which a multitude of long and simple vessels, proceeding 

 in radiating bundles in four or five directions, ultimately disembogue 

 themselves at various points of the skin, each being situated very 

 remotely from each other *. 



Almost all the thickness of the snout of the squalus is occupied by 

 a cellular tissue filled with mucilage, whence proceed the bun- 

 dles of tubes which secrete this mucilage by the pores of the skin, and 

 we there see further, large regular vessels, of which one runs all the 

 length of each side of the body. 



In the cod, there is a large vessel which runs along the whole 

 length of the body, bifurcates behind the eye, proceeds by two 

 branches on each side towards the end of the snout, and gives, at 

 intervals, branches which open into the skin: a smaller one creeps 

 along the preoperculum and the inferior gill. 



The eel and conger have large openings at different points of their 

 snouts, through which those long vessels open that are analogous to the 

 vessels forming in the rays, such regular circular lines ; but each 

 species will offer in this respect differences which it will be requisite to 

 enumerate in its proper article, and we shall content ourselves here 

 with these indications. 



The lateral line of fishes has generally some secretory apparatus 

 which follows its length; this is seen, in particular, very distinctly in 

 the tunny, in which a body of a much deeper red than the rest of the 

 flesh, passes every where beneath the lateral line; this gives off 

 small tubes constituting the pores of the line; each of these small 

 tubes receives a filament of nerve, from the lateral line, there is some- 

 thing very much like it in the carp. 



* Munro, pi. V. 



