If, from some rich collection of armor, of the middle ages, immediately after examining the mighty masses of iron in which our knights of old oppressed and half stifled themselves, we go to the Museum of Natural History, and examine the armor of the Crustacæ, we shall actually feel something very like contempt for our human skill. The former are a mere masquerade of absurd disguises, that seem especially designed for encumbering their warlike wearers, and rendering them impotent. But these latter, especially the armor of the terrible _Decapodes_, the ten-footed warriors of the waters, are so marvellously armed that had they but the stature and bulk of our human warriors, none of us could dare even to look upon them. The _veni vidi_ of Cæsar, would be eternally followed by his soon-ended _Vici_; they would not need to seize, or to strike; their very aspect would thrill, magnetise--utterly stupefy and subdue us. There they are, all ready for the fight, armed at all points. Within that terrible arsenal, offensive and defensive, how lightly, yet how strongly are they armed. There are the strong nippers, mandibles, ready to craunch through iron itself, and the cuirasses, furnished with the thousand darts, every one of which cries aloud to the foe _Noli me tangere_. We ought to be very thankful to Nature, that has made them thus diminutive. If only the stature and bulk of man were given to them, who, who, and by what means, could engage with them? Fire arms would be in vain; the Elephant, vast and mighty, and intelligent as he is, would have to hide; the fierce Tiger, with lashing tail, blood-shotten eyes and fatal paw, would seek shelter on the topmost branches of the tallest trees, and the trice solid hide of the Rhinoceros, would no longer be invulnerable. We perceive at once that the interior agent, the motive power of that machine, centralized within an almost invariable convex, has, even from that single peculiarity, a perfectly enormous force. The slender and delicate elegance of man, his longitudinal figure, divided into three parts, with four great and diverging appendages, distant, all, from his centre, make him, whatever we may say to the contrary, an essentially weak animal. In those armors of the old knights, in the great, telegraphic arms, and in the heavy, pendant legs, we, at a glance, see, and sadden, as we see, the unsteady, uncentralized creature; halting and staggering, that the slightest collision will beat to the earth. In the crustacæ, on the contrary, the appendages are at once so firmly, so neatly, and so closely, conjoined to the short, rounded, and compacted body, that every blow, every touch, every grasp, has the whole weight, and the whole force and impetus of the entire mass. Even to the extremity of its claws, every inch is instinct with nervous energy, mighty with the whole physical force.