A SHORT LECTURE ON FISHES. 



OF all the animals composing that great branch of the animal 

 kingdom called vertebrates, the fishes are the simplest in 

 structure and intelligence, and are the oldest in the history of the 

 globe, as shown by the remains in the rocks. Fishes being des- 

 tined to an active life under water, have all their organs adapted 

 to this purpose — gills instead of lungs, Umbs shaped as fins, and so 

 forth. They differ in form, but all have the simple outline of a 

 large head, no neck, and the body tapering gradually to the end 

 of the tail. Some have no fins, but generally they are present, and 

 arranged in pairs symmetrically, or singly on the back or abdomen. 

 Behind the head are large openings leading to the gills. The 

 water entering the mouth in breathing, is driven across the gills 

 and escapes by these openings. The scales greatly vary, their 

 shape forming one of the characters by which a fish is classified. 

 They are horny plates similar to our finger-nails, containing min- 

 ute, polished plates of color, giving certain fishes a dazzling bril- 

 liancy of tinting that reminds us of gold and silver. 



The skeleton of fishes is either horny or made of cartilage, 

 which is a tough, elastic substance, better known as "gristle." 

 It is composed of a head, trunk and limbs. The head is made up 

 of a large number of bones intricately put together, particularly 

 those supporting the arches of the gills and gill-covers {opercula), 

 the tongue and neighboring parts, which has been termed the 

 hyoid apparatus. Next behind the skull comes a chain of bones 

 called vertebrcB, extending the whole length of the body. Each 

 vertebra is shaped like an hour-glass, and is armed with spines 

 and projections X.exmtA processes, some of which, by interlocking, 

 hold the vertebras more firmly together, while others give a strong 

 attachment to muscles. This chain is the backbone or vertebral 

 column, which, by its presence in every fish, bird, reptile, and mam- 

 mal, unites them into a single group^the Vertebrata. Above the 



