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assistant or auxiliary jaws or jaw-feet. The action of this com- 

 plicated apparatus may very well be seen, when the lobster or 

 crab is eating. He grasps and turns his prey about with the 

 auxiliary jaws , while the fore-pairs are used for biting and 

 chewing. Behind the auxiliary jaws come five pairs of legs , 

 the first three pairs of which end in claws ; the first pair , 

 being of immense size and strength , serves also as a wea- 

 pon of attack and defence. Even under the tail there are se- 

 veral appendages like legs , which in the female , serve to 

 hold the eggs. If we wish to form a Schema of this physical 

 structure, we first take a series of rings or sections lying one 

 behind the other, of which each section carries a pair of lateral 

 members. These members are differently developed in harmony 

 with the principle of division of labour , and partly serve as 

 jaws and weapons, partly as egg- carriers, according to the seg- 

 ment to which they belong. A similar differentiation is shown 

 by the sections themselves, which are partly welded into one 

 piece , partly connected in a manner allowing of freedom of 

 motion. This different ution of originally similar parts gives the 

 measure of the animal's degree of organisation, and therefore 

 we consider the crab to be of a higher order than the Annelid, 

 for example, which is also divided into sections, but they are 

 not highly enough developed to serve for different purposes, at 

 least not in such a pronounced manner. 



If we examine the lobster more closely, we see that he is 

 almost constantly fanning with his feathery jaws, and frequently 

 moves his legs and tail 'appendages in a similar manner. This 

 is his way of breathing, lust as lung-breathing land-animals 

 renew the air in their lungs by the rythmic expansion and con- 

 traction of the lobes of the latter, so the lobster, by the above- 

 named movements, pumps fresh water in to his gills, which are 

 situated at the base of the legs under the breast-plate. 



An important period in the life of crabs and lobsters is when 

 they change their shells, when they may literally be said to creep 

 out of their skins. At such times a crack appears in the hinder 

 edge of the breast-plate, and the lobster slowly pushes its way 

 through this backwards , a troublesome and often dangerous 

 operation , for all the limbs , the thick claws , the eyes , the 

 feelers and mouth-apparatus , must be each drawn out of its 

 narrow case, and even the stomach is skinned ! Very often the 

 animal sacrifices one or both of its big claws , and its soft 

 body is in great danger until the new armour has become har- 

 dened , and then the animal instinctively iries to hide itself 



