HISTORY AND ANATOMY OF THE GOLDFISH 



The ordinary goldfish has two sets of horizontal paired fins, the 

 anterior paired or pectoral fins, Fig. 2, connected with the clavicles and 

 the skull immediately behind the gills, and the posterior paired or ventral 

 fins inserted on the abdominal surface below and to the rear of the pectorals 



FIG. 2 — Skeleton of the Common Goldfish 



and articulated to the posterior visceral arches and the pubic bone. The 

 single median or dorsal fin is interspaced with the upper intersplnous bones; 

 the single anal fin with the lower interspinious bones, and the tail or caudal 

 fin set vertically at the extremity of the spine, articulated so that it is flex- 

 ible in all directions. The rays of all the fins are branched, increasing in 

 number towards their extremities. The spinous and soft rays of the paired 

 fins correspond with the bones of the limbs of other animals, one of their 

 functions being to maintain the balance of the fish. Retrograde motion 

 is principally affected by the pectoral fins which also direct the course of 

 the fish by acting as propellers, further serving as adjuncts to the respi- 

 ratory system in changing the water at the gills. The ventral fins act as 

 a break in checking the forward motion in addition to aiding in the retro- 

 grade movement. The dorsal and anal fins balance the body, and as rud- 

 ders prevent zigzag or rocking motion, while the caudal fin is the principal 

 means of locomotion, and also, together with the anal fin, aids in steering 

 the fish. 



All the fins are organs of motion, but it is by the caudal fin that the 

 fish is impelled forward. If the movement is to be swift, it is strongly 

 bent to the right and left, while a gentle forward motion is effected by an 

 undulating movement, the lobes and rays of the caudal fin, acting like the 

 blades of a screw or an oar in sculling. If the fish wishes to move 

 towards the left. It gives a stroke of the tail to the right, the right pectoral 



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