BREEDING HABITS OF FISH. 159 



water Tvliile the tail is bent; they are then straightened, and 

 it is when being straightened that the fish is propelled. 

 The movements of tlie pectorals and ventrals are to steady 

 the fish and to elevate and de23ress it, while the dorsal and 

 anal fins steady the body and keep it upright, like a dorsal 

 and ventral keel. 



Among viviparous bony fishes are certain Cyprinodonts 

 (as Anableps and Pcecilia), the eel-like Zoarces, and the 

 blind-fish of the Mammoth Cave. A small family of Cali- 

 fornian marine fislies, resembling the sun-fisli (Pomotis), 

 are called by Agassiz Emhiotocidce, from the fact that they 

 bring forth their young alive. Emoiotoca Jachsoni Agassiz, 

 which is twenty-seven and a half centimetres (10^ inches) 

 long, has been known to produce nineteen young, each 

 about seven and a half centimetres (3 inches) long. 



During their breeding season, many bony fishes, such as 

 the stickleback, salmon, and jnke, are more higjily colored 

 than at other times, the males being especially brilliant in 

 their hues. 



Orders of Bont Fishes. 



Order 1. Body long; ventral fins 

 either abdominal or wanting. . . Opisthomi (Notacantbus). 



Order 2, Body long, snake-like, 



no ventral fins Apodes (Anguilla, Eel). 



Order 3. Body broad ; lips witb 

 barbels Nematognathi (Amiurus, Pouts). 



Order 4. Body more or less ob- 

 long (in African rivers) Scyphophoi-i (Mormyrus). 



Order 5. Body usually com- 

 pressed; all the bones and fins 

 well developed Teleocephali (Salmo, Perca, Gadus). 



Order 6. Head and mouth very 

 large; pectoral fins supported 

 by slender bones PediculaU (Lophius, Goose-fish). 



Order 7. Gills tufted; body long 

 and slender LophobranchU (Hippocampus). 



Orders. Bonesof upper and lower 

 jaw united; often rounded and 

 spiny Plectognathi (Tetrodon, Mola). 



