When the Crustaceæ are large they are the tyrants and the terror of both land and sea; their impregnable armor enables them to attack everything. They would multiply to such an excess as to disturb the balance of living creatures, but that their armour itself is their great peril and destroyer. Hard and inelastic, it will not yield to the increasing growth of the animal and thus becomes its prison always, and at certain periods its torture. To find, despite this solid wall, the means of breathing, it is obliged to place the organ of respiration in that very organ, the claw, which it most frequently loses. To allow for the growth of its interior substance, it is obliged--most perilous obligation!--to submit that the hard cuirass shell shall at times be discarded; that the creature shall have its seasons of _moulting_; that the eyes, and the claws, and the tentacles, which supply the place of lungs shall suffer with all the rest. A strange and pitiful sight it is to see the Lobster writhing, twisting, struggling, to get out of its too confining armor. So violent is the struggle that he sometimes actually casts off his claws. Then he remains soft, weak, exhausted. In two or three days a raw shell covers the naked body; but the Crab does not so easily repair damages; it takes him much longer to renew his armor, and during that time he is the victim of all that previously were his unspared and unpitied prey. Even handed justice now becomes terrible to him. The victims now have their revenge; the strong is subjected to the law of the weak; falls, as a species, to their level, and pays full share in the great balance between Life and Death. If one died but once in this world, there would be less of sadness, but every living thing must partially die daily; daily suffer moulting, that partial death which is essential to the continuance of life. Hence, a weakness and a melancholy to which we do not readily confess. But what is to be done? The bird in its moulting time is sad and silent; still more sad is the poor snake when it casts its skin. We, also, in every month, every day, every instant, are parting with portions of our living frame, but as gently as constantly, and only feel weakened, in those moments of dreamy melancholy, when the vital flame is weakened, that it may become stronger and more vivid. How far more terrible it must be for the creature whose whole external frame work must be rent asunder and cast off. It is weak, timorous, crushed;--at the mercy of the first comer. There are crustacæ of the fresh water that must thus partially die a score of times in every two months. Others (the crustacean suckers) succumb to this terrible operation, are unable to renew their armor, and lose all power. So to speak, they resign their piratical commission, and, coward-like, take shelter in the viscera of the larger animals, which, in spite of themselves, have to forage for them and to feed them.