HISTORY AND ANATOMY OF THE GOLDFISH 



fin acting simultaneously while the left remains pressed to the body ; if 

 the motion is to be checked, the ventral fins are erected and expanded 

 vertically ; if the motion is to be retrograde, a backward stroke is made 

 with all the paired fins and the dorsal and anal fins held rigidly upright, 

 the caudal fin being either held on a line with the body or slightly relaxed; 

 and should the retrograde movement be in either direction, the caudal fin 

 is flexed to the opposite side. 



By observing injured fishes the purpose of the fins will be manifested. 

 If a pectoral fin is useless or both a pectoral and a ventral fin on the same 

 side, loss of balance will ensue, the fish falling on the opposite side ; with- 

 out both the pectorals, the head sinks ; without the ventrals, the motion 

 is unsteady; without the dorsal and anal fins the motion is zigzag; with- 

 out the caudal fin, forward movement is labored and slow; and without 

 any of the horizontal and vertical fins, the fish floats helplessly on its back, 

 this being the heaviest part of the body. 



The head and fins of the goldfish are naked, that is, devoid of scales; 

 but the body is covered with an even layer of cycloidal scales which con- 

 sist of thin, flexible, horny discs, almost circular in form and evenly imbri- 

 cated, or overlapping each other like tiles, with the posterior parts extend- 

 ed and free, the anterior parts being embedded 

 in the epidermis and muscular tissue. Fig. 3. 

 They have an enameled surface, showing a fine 

 striation concentric to the margin with stiffening 

 ribs radiating from the rear. Their arrangement 

 is in an oblique transverse section across the body. 

 On each side, reaching from the head to the caudal 

 fin, there is a row of scales different from these in 

 structure, which constitute the lateral line. Each 

 of these scales is perforated by a tube leading to a 

 duct connected with a sac in the head ; their func- 



, . 1 • c 1-1 1 FIG. 3 — Greatly enlarged scale 



tion being the excretion of mucus which covers the of the Goldfish and diagram 

 body to lessen the friction of scales and water, and "fimbrication. 

 to make it impervious thereto. This mucilaginous system is also pro- 

 vided with nerves and is the seat of a peculiar sense which corresponds to 

 the organs of touch and hearing. 



The digestive system of the goldfish is simple and adapted to its 

 natural mixed diet. Fig. 4. Devoid of teeth, a limited mastication only 

 takes place in the throat, which, for this purpose, is provided with a num- 

 ber of bony protuberances. The mouth is formed of the maxillary and 

 the mandible bones, having labial folds or lips. The oesophagus is 



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