and refined as that beauty is, it is clearly brought out.  The flower-like beauty of the egg of the peacock’s parasite, the delicate symmetry and subtle carving of the others, simply entrance an observer.  Note then that it is not merely enlarged specks of form that we are beholding, but such true magnifications of the objects as bring out all their subtlest details.  And it is this quality that must characterize our most powerful lenses.  I am almost compelled to note in passing that the beauty of these delicate and minute objects must not be considered an end—­a purpose—­in nature.  It is not so.  The form is what it is because it must be so to serve the end for which the egg is formed.  There is not a superfluous spine, not a useless petal in the floral egg, not an unneeded line of chasing in the decorated shell.  It is shaped beautifully because its shape is needed.  In short, it is Nature’s method; the identification of beauty and use.  But to resume.  We may at this point continue our illustrations of the analytical power of moderate lenses by a beautiful instance.  We are indebted to Albert Michael, of the Linnean Society of England, for a masterly treatise on a group of acari, or mites, known as the oribatidae.  Many of these he has discovered.  The one before you is a full grown nymph of what is known as a palmicinctum.  It is deeply interesting as a form; but for us its interest is that it is minute, being only a millimeter in length.  But it repeatedly casts the dorsal skin of the abdomen.  Each skin is bordered by a row of exquisite scales; and then successive rows of these scales persist, forming a protection to the entire organism.  Mark then that we not only reveal the general form of the nymph, but the lens reveals the true structure of the scales, not enlargement merely, but detail.  The egg of the organism, still more magnified, is also seen.

To vary our examples and still progress.  We all know the appearance and structure of chalk.  The minute foraminifera have, by their accumulated tests, mainly built up its enormous masses.  But there is another chalk known as Barbados earth; it is silicious, and is ultimately composed of minute and beautiful skeletons such as those which, enormously magnified, you now see.  These were the glassy envelopes which protected the living speck that dwelt within and built it.  They are the minutest of the Radiolaria, which peopled in inconceivable multitudes the tertiary oceans; and, as they died, their minute skeletons fell down in a continuous rain upon the ocean bed, and became cemented into solid rock which geologic action has brought to the surface in Barbados and many other parts of the earth.  If a piece of this earth, the size of a bean, be boiled in dilute acid and washed, it will fall into powder, the ultimate grains of which are such forms as these which you see.  The one before you is an instance of exquisite refinement of detail.  The form from which the