817 



FISH. 



FISH. 



819 



each side, tlie dental portion in front, and the articular portion 

 behind. 



The Palatines (fig. 3, m TO) are extended longitudinally on each side, 

 and form part of the roof of the mouth; they are often furnished 

 with teeth. 



The Opercular Bones. The chief portion of the sides of the head 

 behind the eye consists of the opercular bones : these are generally 

 four in number, and are termed the operculum (fig. 1, g), the sub- 

 operculum (fig. 1, A), the pre operculum (fig. 1, i), and the inter-oper- 

 culum (fig. 1, i). The first of these covers the gills. 



The Branchiostegous Rays (fig. 1, o), which are often mentioned in 

 descriptions, are situated under the opercular bones. 



The Teeth in fishes are almost entirely osseous ; they are usually of 

 a simple spine-like form, and recurved at the tip. Teeth are found 

 in almost every bone in the interior of the mouth ; in the superior 

 and inferior maxillary, and intermaxillary bones ; likewise on the 

 branchial arches, pharangeal bones (which are situated in the throat), 

 and on the tongue. There ia considerable variety in their structure, 

 aa will be found in the various descriptions of fishes found in other 

 parts of this work. 



The Scales are composed of two substances, one resembling horn 

 in its texture, and the other of a harder and bone-like nature; they 

 are generally attached to the skin by their anterior edge, and consist 

 of numerous concentric lamina; (secreted by the skin), the smallest of 

 which is first formed. Certain scales, forming a continuous series, in 

 a slightly waved line from the head to the tail of the fish, are pierced 

 in or near their centre, and furnished with a tube through which a 

 slimy matter is poured, which serves to lubricate the body of the 

 animal. This series of tubes forms a line visible on the sides of the 

 body, and which is termed the lateral line. 



The structure, form, and position of the scales of fishes are very 

 variable, and have furnished M. Agassi/. ( ' Recherches sur les 

 Poissons FoBsiles') with characters for a new classification of these 

 animals. 



As regards the senses, those of taste and touch appear to be but 

 slightly developed in fishes. When we find the tongue thickly covered 

 with teeth (as is often the case), and used as an organ of prehension, 

 and when we consider the quick manner in which the food is swallowed, 

 it would certainly appear that their sense of taste is very slight. The 

 sense of touch is probably most developed in the cirrhi attached to 

 the mouth of those fishes that have them. The long filaments with 

 which the fins of some fishes are furnished also perhaps serve, through 

 the sense of touch, to indicate the vicinity of weeds, or other objects 

 in the water. 



The eyes are differently placed in the various species of fishes, in 

 accordance with their habits : for the most part they are placed 

 laterally, and in some (those that live at the bottom of the water) we 

 find them directed upwards. In some of the species of sharks (those 

 of the genus Zyyitna) they are situated at the end of an elongated 

 lateral process on each side of the head. 



The sight in fishes is acute ; the range of vision however is probably 

 somewhat limited. The eyes (which are furnished with a spherical 

 lens) are generally large, but in some species they are very small, 

 whilst others appear to be destitute of them. 



Although fishes appear uot to possess certain portions of the auditory 

 apparatus, observed in animals of a higher grade, they nevertheless 

 possess the sense of hearing. 



There are reasons for the belief that the sense of smell in fishes is 

 tolerably acute : their olfactory nerves are of large size, and disposed 

 over a considerable extent of surface. 



By far the greater number of fishes are of carnivorous habits ; 

 there are some however which feed upon vegetable substances, and 

 we find the stomach modified accordingly as in other animals. 



The sexes of fishes, if we except the sharks and rays, offer no very 

 decided external characters by which they may be distinguished : as 

 in the higher animals however, observes Mr. Yarrell, "the respiratory 

 organs occupy more space in the males than in the females ; and, on 

 the other hand, the abdomen is larger in the females than in the males : 

 the males may therefore be known from the females by their some- 

 what sharper or more pointed head, the greater length of the gill- 

 cover, and the body from the dorsal fin downwards being not so deep 

 compared with the whole length of the fish." 



The sexual organs of fishes are in the generality of the species of a 

 more simple nature than is observed in the higher orders of the 

 Verttbrala, " consisting, as will be found, towards the season of pro- 

 ducing then- young, of two elongated oval lobes of roe, one on each 

 ride of the body, placed between the ribs and the intestinal canal ; 

 the lobes in the female, called hard roe, contain a very large number 

 of roundish grains, called ova or eggs, which are inclosed in a delicate 

 membranous tunic or bag, reaching to the side of the anal aperture, 

 where an elongated fissure permits egress at the proper time. In the 

 males, the lobes of roe are smaller than in the females, and have the 

 appearance of two elongated masses of fat, which are called soft roe ; 

 they remain however firm till the actual season of spawning, when 

 they become by degrees more and more fluid, aud'the whole is ulti- 

 mately voided by small portions at a time under slight abdominal 

 pressure 



" At tho season for depositing the spawn, which varies with almost 

 NAT. HIST. mv. VOL. IT. 



every genus, some species repair to the gravelly shallows of rivers, 

 and others to the sandy bays of the sea. This movement is called by 

 fishermen ' going to hill,' or ' roading;' other species resort to bunches 

 of weeds. In many instances, when ready to deposit her spawn, a 

 female is accompanied by two males, one on each side a provision 

 of nature which seems intended to secure the impregnation of the 

 largest quantity of ova, and the range of the influence of the male 

 fluid is enormously increased by diffusion in water. The adhesive 

 nature of the surface of each egg supplies the means of attachment 

 to any of the various substances near which it may happen to be left ; 

 and the time required for the appearance of the young fish is very 

 variable, depending upon the species, the season, and its temperature. 

 The young fish is first apparent as a line wound round the central 

 vitelliue portion of the egg, and ultimately escapes by rupturing the 

 external capsule with its tail." 



We now proceed to give an outline of Cuvier's classification of fishes, 

 since it is that which is perhaps most generally adopted : it is never- 

 theless in many respects very artificial. 



Fishes are divided by this author into two series, that of Ordinary 

 Fishes, or Ossei, distinguished by having the skeleton bony ; the 

 osseous matter being disposed in fibres ; the sutures of the cranium 

 distinct; maxillary and intermaxillary bones, either one or both 

 present : and that of the Cartilaginei, or Chondropterygii, distinguished 

 by having the skeleton cartilaginous ; the bones destitute of fibres ; 

 sutures of the cranium indistinct ; maxillary and intermaxillary bones 

 either wanting or rudimentary, their place being supplied by the 

 palatine or vomer. 



These two series are subdivided aa follows : 



Series 1. Oaei. 

 Section 1. Pectinibranchii. 



Order 1. 



Family Percidce. 

 Loricati. 

 Scicenidce. 

 Sparida. 

 Mimidce. 

 Sqnamipinnat i. 

 Scombridve. 

 Tanioidie. 



A canthopterygii. 

 Family Theutyes. 



Pharyngiens labynnihi- 



formes. 

 Mugilidce. 

 Gobiadce. 

 Lophiadw. 

 Labridce. 

 Centriacidie. 



Order 2. Malacopterygii. 



I. Abdominales. 

 Family Cyprinidte. 

 Esocidce. 

 Siluridie. 

 Salmonidie. 

 Clupeidce. 



2. Subbrachialcs. 

 Family Gadidce. 



Pleuronectid(e. 



Discoboli. 



Echeneididie. 



Order 3. Apodes. 

 Murcenidui. 



Section 2. Plectognathi. 

 Gymnodontidw. 

 Sclerodermi. 

 Section 3. Lophobrancldi. 



Syngnathidce. 



Series 2. Cartilaginei, or Chondropterygii. 



Order 1. Ekutheropomi. 



Sturionidce. 



ChiniGridce. 



Order 2. Plagiostomi. 



Squalida. 



Raiidcz. 



Order 3. Cycloslomi. 



Pteromyzidce. 



The characters of the two great series or sections into which fishes 

 are divided, it has been shown, are taken from the nature of the 

 skeleton. It remains for us now to make a few observations upon 

 the minor subdivisions. 



In the Oaei, or bony fishes, there are three sections. Those of the 

 first, the Pectinibranchii, possess the following characters : Branchiae 

 in continuous pectinated ridges, furnished with an opercular and 

 branchiostegous membrane ; jaws complete and free. Section 2, 

 Plectognathi : Branchias with the pectinations continuous ; opercule 

 and rays concealed beneath the skin ; external aperture a simple cleft ; 

 jaws incomplete ; maxillary firmly attached to the side of the inter- 

 maxillary, which alone forms the jaw ; palatine arch united to the 

 cranium by suture, and immovable. To this section belong the globe- 

 fishes, file-fishes, &c. Section 3, Lophobranchii : -Branchiae in small 

 tufts ; opercule large, confined on all sides by a membrane, with only 

 a small hole for the external aperture ; branchiostegous rays rudi- 

 mentary ; jaws complete and free. To this section belong the pipe- 

 fishes, hippocampus, &c. 



The two latter sections contain but a limited number of species : 

 the Pectinibranchii, ou the contrary, contain all the ordinary and 

 typical fishes, and, as is seen in tho foregoing list, is subdivided 

 into three orders. The fishes of the first of these orders, the 



3 o 



