CHAPTER XXX 



THE ALLIES OF THE PERCH: PISCES 



Halcyon prophecies come to pass 

 In the haunts of bream and bass. 



Maurice Thompson 



Definition of Pisces (Lat. piscis, "fish"). The perch is a 

 member of the class Pisces. Fishes are cold-blooded verte- 

 brates, adapted to life in the water. In the lower forms the 

 notochord persists as a continuous rod ; in the higher fishes 

 it is replaced by the vertebrae. The body is covered with 

 a skin, in which are numerous mucous glands. Scales are 

 usually present, set in pouches in the skin. In the great 

 majority of forms, gills are the only organs of respiration. 

 Locomotion is usually effected by means of fins. With very 

 few exceptions, fishes lay eggs from which the young are 

 hatched ; that is, they are oviparous. Some of the sharks 

 as well as some of the higher fishes produce living young. 



Sharks and Rays. The sharks and rays, or Elasmobran'chii 

 (Gr. elasmos, "metal plate"; branchia, "gills"), are fishes 

 with a cartilaginous skeleton and with gills which commu- 

 nicate with the surface by several openings, instead of being 

 covered by an operculum, as in the perch. The tail is usually 

 unequally lobed, the dorsal division being the larger. 



The sharks (Fig. 163) are, with the exception of one 

 species found in Lake Nicaragua, marine animals, and are 

 developed to the greatest extent in the tropics. The rays, 

 or skates, are more flattened forms, adapted to a life on 

 the bottom of the sea, which they often resemble in color. 

 Fig. 164 shows a species common on the North Atlantic 



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