ICHTHYOLOGY. 



237 



Conclusion, the Baltic. Both these animals are very tenacious of life, 

 ^"'"Y''*^ and will live many days out of water. 



P. planeri. About ten inches long ; greatly resembles 

 the preceding ; but the two dorsal fins are united. It is 

 also an European river fish. 



The other species described by Shaw appear to be but 

 mere varieties of the above. 



Genus Myxine, Linn. This genus is properly separat- 

 ed from the lampreys, to which, however, it has much 

 resemblance. It is distinguished by having only two spi- 

 racles, and by wanting eyes. The species best known, 

 Mijxiiie glutinosa, Linn., or glutinous hag, was classed by 

 Linnaeus with the Vermes ; but its real place is among 

 chondropterygian fishes. The mouth is a membranous 

 ring, with a single tooth on its superior part ; while the 

 strong dentations of the tongue are arranged in two rows 

 on each side, so as to give to these animals the appearance 

 of having lateral jaws, like insects or nereides ; but the 

 rest of their structure corresponds with Petromyzon, and 

 their tongue in particular performs the office of a piston in 

 exhausting the mouth, so as to enable them to adhere to 

 other bodies, like the lamprey. The lips are furnished with 

 eight cirrhi, and above is an aperture commiuiicating with 

 the mouth ; the body is nearly cylindrical, and terminates 

 in a fin which surrounds the tail. The intestine is simple, 

 wide, and straight, as viewed externally ; but it is plaited 

 within : the liver has two lobes : the eggs grow to a con- 

 siderable size. When taken and confined in a large glass 

 jar, a single fish will pour so much mucus from its lateral 

 pores as to give the water the appearance of jelly. 



Three species are known, which Cuvier makes the types 

 of a corresponding number of sub-genera, as follows : 



\st, Heptatremus, Dumer. With seven branchial 

 apertures, as in the lamprey. This animal is the M. Dom- 

 beyi, found on the coast of South America by Dombey. It 

 has a rounded head ; the teeth are sharp, and arranged in 

 two rows, respectively of fourteen and twenty-two, and 

 with one longer than the rest in the upper part of the 

 mouth ; tail rounded at the extremity, and terminated by 

 a very shallow fin. 



2(/, Gastrobranchus, Bloch. The intervals of the 

 branchial rays open into a common canal for each side, 

 and these two canals terminate in two apertures under the 

 heart of the animal, about one third of its length from 

 the head. 



The only known species is the European Myxine gluti- 

 ttosa, Linn. On the Yorkshire coast the fishermen occa- 

 sionally find that it has entered the mouths of fish on the 

 hooks of the long lines, and devoured the flesh, leaving 

 only the skin and bones. They often catch it in the fish 

 thus emptied, and term it the sea-hag. It grows to the 

 length of six or eight inches. 



3d, Ammocjetes, Dumer. Is destitute of a real skeleton ; 

 body cylindrical, with numerous annular lines around it, 

 that give it much the appearance of a worm. It lives in 

 the mud of rivers. Mouth cirrhated, toothless, lobated be- 

 low, and incapable of adhering by suction to other bodies ; 

 fins very shallow ; tail sharp at the tip ; no tracheal tube, 

 as in the rest, but the gills receive water from the oesopha- 

 gus. The only species is P. bra?ichialis, Shaw, the Pride 

 of Pennant, which grows to six or eight inches long, and 

 is as thick as a goose-quill. It inhabits the rivers of Ox- 

 fordshire, and occurs in various parts of tlie European con- 

 tinent. 



We have now brought our exposition of the modern 

 system of Ichthyology to a close. The subjects of which 

 it treats are of deep and sustaining interest, in a philoso- 

 phical point of view, and of the highest and most imme- 

 diate importance when considered in relation to the eco- 

 nomical advantages derivable bji the humaa race. We 



have endeavoured to combine with the precise and tech- Conchisicni. 

 nical expression of the generic and other characters such ^"■•~,-^~-' 

 miscellaneous information as could be collected from au- 

 thentic sources, with a view to render the subject more 

 palatable to the general reader ; — and if any great defi- 

 ciency in that department is observable, we hope it may 

 in some measure be attributed to the nature of this 

 branch of natural history, the objects of which inhabiting 

 another element from ourselves, have thus their on-goings 

 too often veiled from mortal sight by a " world of waters," 

 — which no eye can pierce but the eye of Him who call- 

 ed the light out of darkness, and who created the " hea- 

 vens and the earth, the sea, and all that in them is." 



We shall conclude with a brief allusion to a subject of 

 the highest interest to the naturalist, — one to which we 

 believe no reference has been made in the introductory 

 portion of the present treatise, and which, we regret, our 

 now exhausted space must prevent us from exhibiting at 

 greater length, — ^we mean the geographical distribution 

 of fishes. Our knowledge of the laws which regulate that 

 distribution is meagre in the extreme ; in other words, 

 the facts concerning their true localities are few, and 

 have never been properly generalised. From the immea- 

 surable extent and continuous nature of the fluid which 

 they inhabit, they are supplied by nature with greater faci- 

 lities of dispersion than most other animals ; and the greater 

 equality of the temperature of water, compared with that ot 

 earth or air, admits in several instances of the same spe- 

 cies inhabiting almost every latitude from pole to pole. 

 Those races especially, which, travelling together in vast 

 shoals, speedily consume the natural food which each par- 

 ticular spot affords, are obliged, like the pastoral tribes of 

 old, or the woodland hunters of America, to remove from 

 place to place in search of additional supplies ; and thus 

 the species acquires a more widely extended distribution. 

 It is thus that the cod and herring are spread over the 

 whole extent of the Northern Ocean, and in undiminished 

 numbers, notwithstanding the war of extermination which 

 man and other voracious animals appear to wage against 

 them. Those species which lead a solitary, and, as it may 

 be called, a stationary life, are frequently confined within 

 very narrow limits. The Chaetodons, for example, which 

 delight in rocky coasts covered with madrepores, attach 

 themselves to the torrid zone, which produces so abun- 

 dantly those magnificent ornaments of the sea. But 

 though thus confined to particular spots, from which the 

 individuals of the species seldom wander, the species itself 

 may be said to be repeated again in different regions, se- 

 parated from each other by almost insurmountable obsta- 

 cles. Thus many of what may be termed stationary spe- 

 cies are found identically the same along the coasts of 

 Brazil, in the Arabian Gulf, and over the multiplied 

 shores of Polynesia. It has hence been concluded, that 

 such species, incapable of colonizing themselves by leaving 

 their accustomed shores, and hazarding a journey across 

 unknown oceans, have either been created in more places 

 than one, or have been enabled to transport themselves by 

 means different from any of those that are now available in 

 the ordinary course of nature. 



If the natural means by which the more powerful species 

 inhabiting the saline waters of the ocean have spread them- 

 selves from clime to clime, be to a certain extent within 

 the reach of our comprehension, it is otherwise with those 

 peculiar to rivers, and the waters of inland lakes. How 

 these have contrived to migrate from one region to ano- 

 ther, and to people with identical species the depth of far- 

 removed and solitary waters, separated from each other by 

 chains of lofty mountains, or wide extended wastes of de- 

 sert sand, is a problem which, in the present state of our 

 knowledge, we seek in vain to solve. It may indeed at 

 times happen that spawn or ova are carried by water-fowl 



