202 THE STUDY OF ZOOLOGY vn 



followed by six pairs of jaws folded against one 

 another over the mouth, and five pairs of legs, the 

 foremost of these being the great pinchers, or 

 claws, of the lobster. 



It looks, at first, a little hopeless to attempt to 

 find in this complex mass a series of rings, each 

 with its pair of appendages, such as I have shown 

 you in the abdomen, and yet it is not difiicult to 

 demonstrate their existence. Strip off the legs, 

 and you will find that each pair is attached to a 

 very definite segment of the under wall of the 

 body; but these segments, instead of being the 

 lower parts of free rings, as in the tail, are such 

 parts of rings which are all solidly united and 

 bound together ; and the like is true of the jaws, 

 the feelers, and the eye-stalks, every pair of which 

 is borne upon its own special segment. Thus the 

 conclusion is gradually forced upon us, that the 

 body of the lobster is composed of as many rings 

 as there are pairs of appendages, namely, twenty in 

 all, but that the six hindmost rings remain free 

 and movable, while the fourteen front rings be- 

 come firmly soldered together, their backs forming 

 one continuous shield — the carapace. 



Unity of plan, diversity in execution, is the 

 lesson taught by the study of the rings of the body, 

 and the same instruction is given still more em- 

 phatically by the appendages. If I examine the 

 outermost jaw I find it consists of three distinct 

 portions, an inner, a middle, and an outer, mounted 



