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in an aquarium jar. At the extreme end of the tail there is abroad, 

 notclied tin which aids the tail in propelling and steering the body. 

 We will call this the tail or caudal fin (Fig. 104, B). In most of 

 our common tishes there are seven tins, — six without the caudal. 

 The first of these six is a large tin situated near the middle of the 

 back. This is the hack or dorsal tin (Fig. 104, A) Sometimes we 

 may iind a iish that has two dorsal tins. In this case the one nearest 



4/ 



the head is called first dorsal and the next one behind it the second 

 dorsal. Is^ear tlie head, in a position corresponding to our arms, is a 

 pair of fins which are called the amn or jX'Gtoral fins (Fig. 104 E). 

 Still farther towards the tail, on the under side of the fish, is another 

 pair, corresponding in position to tlie hind legs of a quadruped. 



This pair is called the leg or jyelvic fins 

 (Fig. 104, D). Just behind the pelvic 

 fins is a single fin, situated on tlie 

 middle line of the body. This is the 

 anal fin (Fig. 104, C). The pectoral 



10\.— Diagram of a fish to shoic: and pelvic fins are called paired fins 

 A, dorsal fin; B, caudal ^^^^^^ ^j^^^^^ ^^^.^ .^^ .^.^^ ^.j^^ ^^j^^^.^ 



fin; C, anal fin; J), • . . i, , _t 



pehic fins; E, pectoral winch are nut m pairs are called median 



fins ; L, lateral line. fins, l)ecause they are situated on the 



middle line of the body. Tiie paired fins serve as delicate balancers 

 to keep the l)ody right side up and to regulate speed. They are 

 also used to propel the body backwards. After naming the different 

 fins of the fish in the schoolroom aquarium, it will be interesting 

 to observe the uses of each. 



On the side of the body, extending from the head to the caudal 

 tin, is, in most fislies, a line made up of a series of small tubes 

 which open upon the surface. This is called the lateral line^ and 

 acts in the capacity of a sense organ (I'ig. 104, L). Is the lateral 

 line straight or curved? Does it curve upwards or downwards'^ 

 Does the curvature differ in different kinds of fishes? Do all the 

 fishes you find possess a lateral line ? Is the lateral line complete in 

 all fishes, — i. e., does it extend from the head to the caudal fin 

 without a single break ? 



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