THE ANIMAL CLIMAX-THE CHORDATES 



291 





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Fig. 13-14. Sea bat (ray) lying on the deck of the A/botross. Note its huge pectoral fins that give it the appearance 



of flying when it swims. 



ray. Modified muscles are so constructed 

 as to produce an electrical potential suf- 

 ficiently high to stun lower forms and to 

 cause a good deal of pain in larger animals. 

 Shocking devices are not confined to the 

 rays alone, but are also found among a few 

 higher fish, namely, several species of eels 

 and catfishes. The mechanism of this device 

 has not been completely worked out. 



THE MODERN BONY FISHES 



The cartilaginous fishes, the sharks and 

 rays (class Chondrichthyes ) , developed 

 appendages and true jaws as important ad- 

 juncts to success in the water. Once these 

 became established as a permanent part 

 of the anatomy of aquatic vertebrates, a 

 great deal of "experimentation" apparently 

 ensued. The result was the modern bony 

 fishes (class Osteichthyes ) which have 

 gone "all out" in exploring possible body 



shapes, sizes, and colors that best suit them 

 for their particular aquatic niches. They 

 range from ordinary fish such as the com- 

 mon perch (Fig. 13-17) to the vicious gar- 

 pike (Fig. 13-15) and bizarre sea horse 

 (Fig. 13-16). Obviously they have been 

 highly successful, for they have penetrated 

 virtually every aquatic environment. They 

 are found in the oceans of the world — from 

 the surface to great depths, where they have 

 attained the most weird shapes and have de- 

 veloped extraordinary luminescent organs. 

 In fresh water they are found in swift mov- 

 ing streams as well as stagnant pools. Some, 

 such as the salmon and eel, can survive 

 satisfactorily in either fresh or salt water 

 and migrate seasonally from one environ- 

 ment to the other in connection with their 

 breeding cycle. 



Structurally, the bony fish are similar to 

 the sharks with a few minor exceptions. For 

 example, they have reduced the number of 



