vi.] ON THE STUDY OF ZOOLOGY. 85 



ending in front in a sharp spine, on either side of which are 

 the curious compound eyes, set upon the ends of stout movable 

 stalks. Behind these, on the under side of the body, are two 

 pairs of long feelers, or antennae, 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 diffi 

 cult 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 hind 

 most rings remain free and movable, while the fourteen front 

 rings become 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 emphatically 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 upon a common stem; and 

 if I compare this jaw with the legs behind it, or the jaws in 

 front of it, I find it quite easy to see, that, in the legs, it is the 

 part of the appendage which corresponds with the inner division, 

 which becomes modified into what we know familiarly as the 

 &quot;leg,&quot; while the middle division disappears, and the outer 

 division is hidden under the carapace. Nor is it more difficult 

 to discern that, in the appendages of the tail, the middle division 

 appears again and the outer vanishes ; while, on the other hand, 



