28 NATURALIST'S CABINET 



How to know their age Mode of dying. 



Two methods have been devised tor determin- 

 ing the age of fish; first, by the circles of the 

 scales; secondly, by the transverse section of the 

 back bone. When a fish's scale is examined by 

 a microscope, it is found to consist of a number 

 of circles one within another, in some measure 

 resembling those which appear on the transverse 

 section of a tree, and is supposed to give the 

 same information. For, as the age of trees can 

 be told by the number of their circles; so that 

 of fish may be conjectured by the number of 

 circles in every scale, reckoning one ring for 

 every year of the animal's existence. The age 

 of fish that want scales may also be known by 

 separating the joints of the back-bone, and then 

 minutely observing the number of rings which 

 the surface, where it was joined, exhibits. The 

 Kev. Mr. White gives the following account of 

 the death of a fish. As soon as one dies, the 

 head sinks lower and lower, and the animal 

 stands, as it were, upon it, till becoming weaker 

 and losing all poise, the tail turns over, and at 

 last it swims on the surface of the water, with its 

 belly upwards. The reason why fish, when dead, 

 float in that manner is obvious; because, when 

 the body is no longer balanced by the fins of the 

 belly, the broad muscular back preponderates 

 by its own gravity, and turns the belly upper- 

 most, as lighter, from its being a cavity. 



Voracity is the chief characteristic of these 

 aquatic animals. In most of them, the maw is 



