The Life of the Fish 9 
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 
