In the ocean depths we find that the marine worms, which constitute in the beauty of their appearance a magnificent assemblage, tunnel the upper crust of the bottom. Some years ago the moat or ditch surrounding Fort Jefferson, Fla., was pumped out, leaving a space nearly half a mile in extent, high and dry, which abounded in specimens that would have delighted the eyes of a specialist in any branch. Over this spot we had often, as a lad, enjoyed the venturesome fun of riding upon the backs of the great sea-turtles, kept there for the commissaries’ use, had fished in every nook and corner, and now the opportunity was presented for penetrating below the surface of the bottom. Some little digging showed, that, for a foot or more from the surface, the sand and mud was fairly alive with a variety of worms, numerous to an extraordinary extent, and in many cases beautiful beyond description. This condition of things is true, to a greater or less extent, in many localities; the worms retiring to the mud and other retreats during the day, at night venturing out, and even swimming at the surface. If we take a drop of water from any ditch or pond, or even from the stem of a flower that has been standing in a vase, and place it under a microscope of even ordinary power, we shall find that it is a world of itself; a vast ocean, in fact, to the many forms that live there. Chief among these drop inhabitants, we notice numbers of little creatures that attract attention immediately. They resemble tall hats without brims, or crystal bags with fringed edges. And that they are busy bodies is at once evident, as they swim along at a wonderful rate of speed, eating as they go, keeping their fringes or _cilia_, which appear like so many arms, in perpetual motion; now bumping against each other, forcing their way among crowds of different animals, and always appearing full of life and energy. These little creatures, invisible to the naked eye, are minute worms, or Rotifers; and among them we find some interesting light-givers. The _Synachata_ is one; and others described by Ehrenberg, the largest being about one-eighth of a line in size, present a striking appearance under the glass in a dark room,--the little bags, seemingly at a white heat, darting about in every direction. As small as are these wonderful creatures, they are well worthy of study; and even those not interested in natural history will find that the stems of their flowers, or the water in the vase, contain more wonders than they had dreamed of,--a single drop that can be lifted upon a pin-head being sufficient for the purpose.