io The Life of the Fish 



known as soft rays, are made up of many little joints, and most 

 of them branch and spread out brush-like at their tips. In the 

 fin on the back the first ten of the rays are spines, the rest are 

 soft rays. In the fin under the tail there are three spines, and in 

 each fin at the breast there is one spine with five soft rays. In 

 the other fins all the rays are soft. 



The fin on the back is called the dorsal fin, the fin at the end 

 of the tail is the caudal fin, the fin just in front of this on the 

 lower side is the anal fin. The fins, one on each side, just behind 

 the gill-openings are called the pectoral fins. These correspond 

 to the arms of man, the wings of birds, or the fore legs of a turtle 

 or lizard. Below these, corresponding to the hind legs, is the 

 pair of fins known as the ventral fins. If we examine the bones 

 behind the gill-openings to which the pectoral fins are attached, 

 we shall find that they correspond after a fashion to the shoulder- 

 girdle of higher animals. But the shoulder-bone in the sunfish 

 is joined to the back part of the skull, so that the fish has 

 not any neck at all. In animals with necks the bones at the 

 shoulder are placed at some distance behind the skull. 



If we examine the legs of a fish, the ventral fins, we shall 

 find that, as in man, these are fastened to a bone inside called 

 the pelvis. But the pelvis in the sunfish is small and it is placed 

 far forward, so that it is joined to the tip of the " collar-bone" of 

 the shoulder-girdle and pelvis attached together. The caudal 

 fin gives most of the motion of a fish. The other fins are mostly 

 used in maintaining equilibrium and direction. The pectoral 

 fins are almost constantly in motion, and they may sometimes 

 help in breathing by starting currents outside which draw water 

 over the gills. 



The Skeleton of the Fish. The skeleton of the fish, like that 

 of man, is made up of the skull, the back-bone, the limbs, and 

 their appendages. But in the fish the bones are relatively 

 smaller, more numerous, and not so firm. The front end of the 

 vertebral column is modified as a skull to contain the little 

 brain which serves for all a fish's activities. To the skull are 

 attached the jaws, the membrane bones, and the shoulder- 

 girdle. The back-bone itself in the sunfish is made of about 

 twenty-four pieces, or vertebrae. Each of these has a rounded 

 central part, concave in front and behind. Above this is a 



