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CHAPTER VIII. 



FISHES. 



IN reviewing the series of animals which compose 

 each great division of this kingdom of nature, 

 we constantly find that the simplest structures 

 and modes of progression are those belonging to 

 the aquatic tribes. Among vertebrated animals, 

 the lowest rank is occupied by Fishes, a class 

 comprehending an immense number of species, 

 which are all inhabitants of the water, which 

 exhibit an endless variety of forms, and open to 

 the physiologist a wide field of interesting re- 

 search. We cannot fail to perceive, on the most 

 cursory glance, the beautiful adaptation of the 

 form and structure of all these animals to the 

 properties of the element in which they are 

 destined to reside. In order that the fish might 

 glide through the fluid with the least resistance, 

 all its vital organs have been collected into a 

 small compass, and the body has been reduced 

 into the shape of a compact oval, compressed 

 laterally, and tapering to a thin edge, both before 

 and behind, for the purpose of readily cleaving 

 the water as the fish darts forward, and also of 

 obviating the retardation that might arise from 





