8 THE COMMERCIAL SEA FISHES OF 



sides are generally smooth, and often covered with scales, 

 which will be considered further on. 



A fish, such as a carp, is provided with fins for locomo- 

 tion, and has the vertical ones in three principal situations, 

 and unpaired : the back or dorsal fin, which may be sub- 

 divided into two or three ; one at the end of the tail or the 

 caudal ; and one, which may be subdivided into two or 

 more, behind the vent, termed the anal. There also exist 

 paired fins, one pair in the region of the breast or pectoral, 

 corresponding with the anterior extremities of the higher 

 vertebrates ; while a second or ventral pair represent the 

 legs or hind limbs. The dorsal and anal fins increase the 

 extent of the lateral surface of the fish, by which means 

 they act as a check against lateral oscillations, or a tendency 

 to turn belly up. If these fins are removed, the fish reels 

 about first to one side and then to the other. The caudal 

 assist the velocity with which a fish is proceeding, and this 

 is most apparent in such as have this fin forked. The 

 pectoral is extended from the body, will act like a rudder, 

 and turn the body in a curve towards that side. The 

 ventrals being horizontal, serve to balance the body, and 

 when only one fin acts to incline it to one side, while the 

 two being in motion together can elevate or depress the 

 fish. 



If we examine the composition of these fins, we find in 

 the bony fishes two distinct forms of rays the one being 

 spinate, consisting of spines destitute of any transverse 

 articulations, and with a hard and sharp extremity ; the 

 other being softer, and composed of numerous pieces 

 articulated together and possessing a similar soft ex- 

 tremity. 



But though we can assert that as a rule fins are composed 

 of spines, rays, and an inter-spinous or inter-radial mem- 



