322 SEASIDE DIVINITY. 



where it is perfect, has the effect of causing any 

 body immersed in a fluid to remain in one and 

 the same place without sinking or ascending. An 

 increase of the weight of the body in relation to 

 the water causes it to descend, while a diminution 

 of its relative gravity obliges it to rise toward the 

 surface. Now, many fishes are furnished with an 

 internal piece of mechanism, by which they are 

 able in an instant to alter their specific gravity, 

 and to ascend or descend without employing 

 either fins or tail. This apparatus is called the 

 air-bladder. It consists of a membraneous bag, 

 filled with air secreted by the fish. This bag is 

 surrounded with muscles, on which the fish can 

 act at will. By relaxing those muscles the blad- 

 der becomes larger, the body is therefore speci- 

 fically lighter, and ascends upwards ; by pressing 

 on the bladder with the muscles its size is di- 

 minished, and the animal sinks. This apparatus, 

 although possessed by a great variety of fishes, is 

 not universal. Many of those which live at the 

 bottom of the water are not furnished with it, and 

 for the obvious reason that they do not par- 

 ticularly require it. It is impossible not to per- 

 ceive that this part of the animal's organisation 

 proceeds from the express design of an Intelligence 

 to whom are fully known those laws to which it is 

 so wisely and accurately adjuste.d. 



The gills, or apparatus for respiration in fishes, 

 present a singularly beautiful adaptation of means 

 to the end in view. These organs consist of 

 arches on each side of the head, to which are 



