y NATURAL HISTORY. 



overlapping anterior process of the next succeeding vertebra. The transverse processes are short 

 in the Salmon and Herring, but very long in the Cod family. As these transverse processes 

 approach the tail they bend down and form a canal which arches over the blood-vessels in exactly 

 the same way as the neural arch protects the spinal cord. The ribs of fishes sometimes articulate 

 with the ends of the transverse processes, occasionally beneath them, and sometimes behind them, 

 but the ribs are not united to a sternum, as is the case in the higher Vertebra ta. A considerable 

 number of fishes, such as Globe-fish, Sun-fish, and Pipe-fish have no traces of ribs. The most 

 singular example of vertebrae becoming blended together is seen in the neck of the Pipe-fish (Fistu- 

 laria), in which four neck vertebrae are united into a mass like the sacrum in birds. A true sacrum, 

 however, occasionally exists, as in the Turbot, where two vertebrae are blended together, and in other 

 fishes, like the genus Loricaria, a longer sacrum is developed. The number of vertebrae in osseous fishes 

 is smaller than in the cartilaginous fishes. In the genus Gymnotus, however, there are 236, but in the 

 Sun-fish Sir K. Owen enumerates only eight abdominal vertebrae, and eight in the tail. In the 

 American bony Pike the vertebrae have the bodies convex in front and concave behind, but no fish 

 is known in which the reverse condition of the cup in front and ball behind is met with. Often 

 in fossil fishes the bodies of the vertebrae are unossified, while the neural arches are well developed. 

 Then the notochord is said to be persistent, and occasionally it is sheathed in rings of bone. 



The muscles of fishes are arranged on each side of the body in a series of successive flakes, 

 which correspond in number with the vertebrae. Each of these flakes is attached by its 

 inner border to the corresponding region of the skeleton and by its outer border to the skin. 

 Each muscle or flake is contained in a sheath of connective tissue, which dissolves when the fish is 

 boiled, so that the flakes then readily separate. The fibres of each muscle-flake run straight and nearly 

 horizontally from one partition to the next, so that they extend longitudinally in the length of the 

 fish. In the tail especially these muscles overlap each other, so as to present the same conical form 

 at their ends as is seen in the tails of Crocodiles and Lizards. There are longitudinal divisions of the 

 muscles in most osseous fishes which correspond more or less closely with those observed in the fish- 

 like Batrachia and Ophidia. Towards the head these muscles become specially modified. Both the 

 jaws in fishes are movable as a rule ; and the large square muscle which draws the mandible back- 

 ward stretches from the tympanic region to the maxillary bone, and by another branch to the 

 coronoid process of the lower jaw. This muscle tends to open the fish's mouth. Other muscles 

 widen the back of the mouth, and contract the branchial cavity. There is a series of muscles attached 

 to the hyoid apparatus and the opercular bones by which the requisite muscular movements necessary 

 to respiration are brought about. The branchial arches are similarly supplied with muscles. The 

 muscles of the pectoral fin are arranged in two layers on each side ; the fibres run in opposite 

 directions, so as to cross each other. The inner pair retracts the fin, drawing it back so as to touch 

 the side of the body. The outer pair extends the fin or moves it in the opposite direction. Then 

 there are special muscles for depressing and raising the fin. Similar muscles conti-ol the ventral fins. 

 Muscular fibres act upon the rays, and there are muscles to expand the rays and move the fins in the 

 various directions which they are capable of taking. The median fins have three or four pairs of 

 small muscles attached to each ray, and by these the rays are elevated and depressed. The caudal fin 

 is moved by three series of muscles, but the variations in the muscular system of fishes are extremely 

 numerous. The sucker of the mouth of the Lamprey is worked partly by a circular muscle, termed a 

 sphincter, like that which closes the mouth or the eye in man, and partly by a series of muscles 

 connected with the hyoid cartilage and with the lateral muscles of the body. The Trunk-fish, which 

 is sheathed in bone, and is therefore incapable of lateral movement, has the longitudinal muscles of 

 the body reduced to a thin layer. The muscles attain their greatest development among the Sharks. 

 In fishes the substance of the muscle is usually colourless, owing to the small quantity of blood which 

 it contains ; but in some Sharks and the Sturgeon the muscles of the pectoral fins and the caudal 

 extremity are deeply coloured, and nearly all the muscles of the Tunny are red, like those of mammals. 

 The orange-red colour of the flesh in the Salmon and Charr is not due so much to the colour of the 

 blood as to a peculiar oil which exists in the sheaths of the muscular fibres. 



The skin is tightly stretched over the body in fishes, and enjoys but little sensibility, through 

 being, for the most part, clothed with scales. In the Lamprey the skin consists of two layers, with 



