110 ' VEETEBKATES: FISHES. 



FISHES. 



Fishes are vertebrates which have cool blood, and 

 live wholly in the water, and breathe by means of gills. 

 Most of them are scaly, but some are covered with a 

 smooth skin, others have spines, and others still are cov- 

 ered with bony plates. The jaws are generally armed 

 with teeth, and, in many cases, all parts of the mouth 

 also, and even the gullet. Their movements are gen- 

 erally rapid, and their forward motion is mainly pro- 

 duced by the movements of the tail. The parts which 

 correspond to the arms and legs of quadrupeds = are very 

 short, and are called fins; and their use is mainly to 

 balance and direct. The flesh is light-colored or white. 

 In general, the eye of Fishes has no motion, and the 

 pupil is always of the same size, both in light and dark- 

 ness ; and the ear is wholly enclosed by the bones of the 

 head, and hence it is generally believed that they hear 

 only the loudest sounds. They are very voracious, feed- 

 ing mainly upon smaller fishes, and other small animals, 

 which they usually swallow whole. Those which feed 

 on shell-fish crush their food by means of the teeth in 

 the gullet. Most fishes lay eggs ; a few kinds bring 

 forth living young. Nearly all seem to have no care 

 for their young, but eat them as greedily as they do 

 other food. The number of eggs laid by a single fish 

 in one season is often very great, — the Salmon some- 

 times laying twenty thousand, and the Cod more than 

 nine millions ! The colors of Fishes are very beauti- 

 ful, exhibiting a lustre like that of the metals, and the 

 brilliancy of precious stones, and the delicate tints of 

 flowers ; they are indeed the gems of the waters, as the 

 humming-birds are the gems of the air. The wonder- 



