Genealogical Tree

The small branches in the centre indicate the classes of "worms"; the letters P, B, and S indicate the positions of Peripatus. Balanoglossus, and Sphenodon or Hatteria respectively.

There is of course no doubt as to the fact that some forms of life are more complex than others. It requires no faith to allow that the firstlings or Protozoa are simpler than all the rest; that sponges, which are more or less loose colonies of unit masses imperfectly compacted together, are in that sense simpler than jellyfish, and so on. The animals most like ourselves are more intricate and more perfectly controlled organisms than those which are obviously more remote, and associated with this perfecting of structure there is an increasing fulness and freedom of life.

We may arrange all the classes in series from low to high, from simple to complex, but this will express only our most generalised conceptions. For within each class there is great variety, each has its own masterpieces. Thus the simplest animals are often cased in shells of flint or lime whose crystalline architecture has great complexity. The simplest sponge is little more than a double-walled sack riddled by pores through which the water is lashed, but the Venus' Flower-Basket (Euplectella), one of the flinty sponges, has a complex system of water canals and a skeleton of flinty threads built up into a framework of marvellous intricacy and grace. The lowest insect is not much more intricate, centralised, or controlled than many a worm of the sea-shore, but the ant or the bee is a very complex self-controlled organism. More exact, therefore, than any linear series, is the image of a tree with branches springing from different levels, each branch again bearing twigs some of which rise higher than the base of the branch above. A perfect scheme of this sort might not only express the facts of structure, it might also express our notions of the blood-relationships of animals and the way in which we believe that different forms have arisen.

But the wealth of form is less varied than at first sight appears. There is great wealth, but the coinage is very uniform. Our first impression is one of manifold variety; but that gives place to one of marvellous plasticity when we see how structures apparently quite different are reducible to the same general plan. Thus, as the poet Goethe first clearly showed, the seed-leaves, root-leaves, stem-leaves,

and even the parts of the flower-sepals, petals, stamens, and carpels, are in reality all leaves or appendages more or less modified for diverse work. The mouth-parts of a lobster are masticating legs, and a bird's wing is a modified arm. The old naturalists were so far right in insisting on the fact of a few great types. Nature, Lamarck said, is never brusque; nor is she inventive so much as adaptive.

4. Wealth of Numbers.-Large numbers are so unthinkable, and accuracy in census-taking is so difficult, that we need say little as to the number of different animals. The census includes far over a million living species a total so vast that, so far as our power of realising it is concerned, it is hardly affected when we admit that more than half are insects. To these recorded myriads, moreover, many newly-discovered forms are added every year now by the individual workers who with fresh eye or improved microscope find in wayside pond or shore pool some new thing, or again by great enterprises like the Challenger expedition. Exploring naturalists like Wallace and Semper return from tropical countries enriched with new animals from the dense forests or warm seas. Zoological Stations, notably that of Naples, are "register-houses" for the fauna of the neighbouring sea, not merely as to number and form, but in many cases taking account of life and history as well. Nor can we forget the stupendous roll of the extinct, to which the zoological historians continue to add as they disentomb primitive mammals, toothed birds, giant reptiles, huge amphibians, armoured fishes, gigantic cuttles, and a vast multitude of strange forms, the like of which no longer live. The length of the Zoological Record, in which the literature and discoveries of each year are chronicled, the portentous size of a volume which professes to discuss with some completeness even a single sub-class, the number of special departments into which the science of zoology is divided, suggest the vast wealth of numbers at first sight so bewildering. More than two thousand years ago Aristotle recorded a total of about 500 forms, but more new species may be described in a single volume of the Challenger Reports. We speak about the number of the stars, yet more than one

family of insects is credited with including as many different species as there are stars to count on a clear night. But far better than any literary attempt to estimate the numerical wealth of life is some practical observation, some attempted enumeration of the inmates of your aquarium, of the tenants of some pool, or of the visitors to some meadow. The naturalist as well as the poet spoke when Goethe celebrated Nature's wealth: "In floods of life, in a storm of activity, she moves and works above and beneath, working and weaving, an endless motion, birth and death, an infinite ocean, a changeful web, a glowing life; she plies at the roaring loom of time and weaves a living garment for God."

5. Wealth of Beauty.-To many, however, animal life is impressive not so much because of its amazing variety and numerical greatness, nor because of its intellectual suggestiveness and practical utility, but chiefly on account of its beauty. This is to be seen and felt rather than described or talked about.

The beauty of animals, in which we all delight, is usually in form, or in colour, or in movement. Especially in the simplest animals, the beauty of form is often comparable to that of crystals; witness the marvellous architecture in flint and lime exhibited by the marine Protozoa, whose empty shells form the ooze of the great depths. In higher animals also an almost crystalline exactness of symmetry is often apparent, but we find more frequent illustration of graceful curves in form and feature, resulting in part from strenuous and healthful exercise, which moulds the body into beauty.

Not a little of the colour of animals is due to the physical nature of the skin, which is often iridescent; much, on the other hand, is due to the possession of pigments, which may either be of the nature of reserve-products, and then equivalent, let us say, to jewels, or of the nature of waste-products, and thus a literal "beauty for ashes." It is often supposed that plants excel animals in colour, but alike in the number and variety of pigments the reverse is true. Then as to movement, how much there is to admire ; the birds soaring, hovering, gliding, and diving; the monkey's gymnastics; the bat's arbitrary evolutions; the grace of the

fleet stag; the dolphin gamboling in the waves; the lithe lizards which flash across the path and are gone, and the snake flowing like a silver river; the buoyant swimming of fishes and all manner of aquatic animals; the lobster darting backwards with a powerful tail-stroke across the pool; the butterflies flitting like sunbeams among the flowers. But

are not all the delights of form and colour and movement expressed in the songs of the birds in spring?

I am quite willing to allow that this beauty is in one sense a relative quality, varying with the surroundings and education, and even ancestral history, of those who appreciate it. A flower which seems beautiful to a bee may be unattractive to a bird, a bird may choose her mate for qualities by no means winsome to human eyes, and a