266 THE BE"ASON WHY. 



"Speak to the earth, and it shall teach thee; and the fishes of the sea shall 



declare unto thee. Who knoweth not in all these that the hand of the Lord hath 



wrought this." JOB XII. 



1054. Why are the fins of fishes proportionately sc much 

 tmallcr than the icings of birds? 



Because there is less difference between the specific gravity of 

 the body of a fish, and the water in which it moves, than between 

 the body of a bird, and the air on which it flies. The fish, therefore 

 does not require such an expanded surface to elevate or guide it. 



1055. Why have fishes scales? 



Because scales, while they afford protection to the bodies of fish, 

 are conveniently adapted to their motions ; and as the scales present 

 no surface to obstruct their passage throityh the water, as hair or 

 feathers would do, they evidently form the best covering for the 

 acquatic animal. 



1056. Why do fishes float in streams (when they are not 

 swimming) with their heads towards the stream? 



Because they breathe by the transmission of water over the 

 surface of their gills, the water entering at the mouth, and passing 

 over the gills behind. When, therefore, they lie motionless with 

 their heads to the stream, they are in that position which naturally 

 assists their breathing process. 



1057. Why havefishes air-bladders ? 



Because, as the density of water varies greatly at different depths, 

 the enlargement or contraction of the bladder regulates the relation 

 of the specific gravity of the body of the fish to that of the water 

 in which it moves. 



1058. Why have whales a very large development of oily 

 matter about their heads ? 



Because their heads are thereby rendered the lighter part of their 

 bodies, and a very slight exertion on the part of the animal will 

 bring its head to the surface to breathe air, which it constantly 

 requires. 



1059. Why have birds that swim upon water iceb-feet ? 



Because the spreading out of the toes of the bird brings the 

 membrane between the toes into the form of a fin, or water -wing, 



