This seems a fanciful invention, and one quite contrary to good sense; to place the hard and the solid beneath the thick covering of the soft! To place the bone, so useful without, precisely where it seems it must be so useless! The crustaceæ must needs have laughed in derision when they first saw the short, thick, soft fish of the Indian Ocean, for instance, without defensive armor, having no strength save inwardly, protected only by its oily fluidity, by the exuberant mucus that surrounds it, and which by degrees consolidates into elastic scales, a slight cuirass, which ever yielding, never yields entirely. It was a revolution comparable to that of Gustavus Adolphus, when he relieved his soldiery of their heavy iron armor, and covered their breasts only with the at once stout and yielding buff leather. A late revolution, but a wise one. Our fish, being no longer confined like the crab or lobster, imprisoned in armor, is at the same time relieved from the cruel condition inseparable from that armor, the _moulting_, with its attendant danger, weakness, struggle, and enormously wasteful expenditure of strength. Like the superior animals and man, he moults slowly. He economises and hoards up strength, and creates for himself the treasure of a powerful nervous system, with numerous telegraphic threads that connect spine and brain. Even when the bone is soft or absent, and the fish preserves its embryonic appearance, he has nevertheless his great harmony in that abundant provision of nervous threads. We do not find in the fish the elegant weakness of the reptile and the insect, so slender that in those parts one can cut through them as through a thread; his segments are within, and well protected. He uses them for contractile power, but does not, as the less perfect reptile and insect do, expose them to external injury. Like the crustaceæ, the fish prefers strength to beauty, and for this end has no neck; head and trunk form one mass. Admirable principle of strength, which enables him, in cleaving through so yielding an element as water, to strike, at will, with a thousand fold more force than is necessary, and then his motion is as the flight of an arrow or the flash of lightning! The interior bone, single in the Seiche, is in the fish at once one and multiple; one for force of unity, multiple for elasticity, enabling the muscles alternately to contract and expand, and thus create swift motion. Marvellous, really marvellous is that formation of the fish, so solid without and contractile within, that inward keel to which are attached the motor muscles which work with an alternating shock. Exteriorly, he exposes only his auxiliary oars, short fins which are but little in danger, being strong, slippery, and sharp to wound, or to scrape. How superior in all this is the fish, to the Poulpe and the Medusa, which present to all comers soft flesh, a tempting morsel for the crustaceæ or the porpoise.