communicated from one animal to another? When we find that all the members of one zoölogical family, however widely scattered over the surface of the earth, inhabiting different continents and even different hemispheres, speak with one voice, must we not believe that they have originated in the places where they now occur, with all their distinctive peculiarities? Who taught the American thrush to sing like his European relative? He surely did not learn it from his cousin over the waters. Those who would have us believe that all animals originated from common centres and single pairs, and have been thence distributed over the world, will find it difficult to explain the tenacity of such characters, and their recurrence and repetition under circumstances that seem to preclude the possibility of any communication, on any other supposition than that of their creation in the different regions where they are now found. We have much yet to learn, from investigations of this kind, with reference not only to families among animals, but to nationalities among men also.

The similarity of motion in families is another subject well worth the consideration of the naturalist: the soaring of the birds. of prey, the heavy flapping of the wings in the gallinaceous birds, the floating of the swallows, with their short cuts and angular turns, the hopping of the sparrows, the deliberate walk of the hens and the strut of the cocks,-the waddle of the ducks and geese, the slow, heavy creeping of the land-turtle,- the graceful flight of the sea-turtle under the water,-the leaping and swimming of the frog,—the swift run of the lizard, like a flash of green or red light in the sunshine,- the lateral undulation of the serpent, the dart of the pickerel,-the leap of the trout, the rush of the hawk-moth through the air,-the fluttering flight of the butterfly,-the quivering poise of the humming-bird,— the arrow-like shooting of the squid through the water,- the slow crawling of the snail on the land, -the sideway movement of the sand-crab,-the backward walk of the crawfish,- the almost imperceptible gliding of the sea-anemone over the rock,- the graceful, rapid motion of the Pleurobrachia, with its endless change of curve and spiral. In short, every family of animals has its characteristic action and its peculiar voice; and yet so little is this endless variety of rhythm and cadence both of motion. and sound in the organic world understood, that we lack words to express one-half its richness and beauty.

FORMATION OF CORAL REEFS

From Methods of Study in Natural History'

OR a long time it was supposed that the reef-builders inhabited very deep waters; for they were sometimes brought up upon sounding-lines from a depth of many hundreds or even thousands of feet, and it was taken for granted that they must have had their home where they were found: but the facts recently ascertained respecting the subsidence of ocean-bottoms have shown that the foundation of a coral-wall may have sunk far below the place where it was laid. And it is now proved, beyond a doubt, that no reef-building coral can thrive at a depth of more than fifteen fathoms, though corals of other kinds occur far lower, and that the dead reef-corals, sometimes brought to the surface from much greater depths, are only broken fragments of some reef that has subsided with the bottom on which it was growing. But though fifteen fathoms is the maximum depth at which any reef-builder can prosper, there are many which will not sustain even that degree of pressure; and this fact has, as we shall see, an important influence on the structure of the reef.

Imagine now a sloping shore on some tropical coast descending gradually below the surface of the sea. Upon that slope, at a depth of from ten to twelve or fifteen fathoms, and two or three or more miles from the mainland, according to the shelving of the shore, we will suppose that one of those little coral animals, to whom a home in such deep waters is congenial, has established itself. How it happens that such a being, which we know is immovably attached to the ground, and forms the foundation of a solid wall, was ever able to swim freely about in the water till it found a suitable resting-place, I shall explain hereafter, when I say something of the mode of reproduction of these animals. Accept, for the moment, my unsustained assertion, and plant our little coral on this sloping shore, some twelve or fifteen fathoms below the surface of the sea.

The internal structure of such a coral corresponds to that of the sea-anemone. The body is divided by vertical partitions from top to bottom, leaving open chambers between; while in the centre hangs the digestive cavity, connected by an opening in the bottom with all these chambers. At the top is an aperture serving as a mouth, surrounded by a wreath of hollow tentacles, each

one of which connects at its base with one of the chambers, so that all parts of the animal communicate freely with each other. But though the structure of the coral is identical in all its parts with the sea-anemone, it nevertheless presents one important difference. The body of the sea-anemone is soft, while that of the coral is hard.

It is well known that all animals and plants have the power of appropriating to themselves and assimilating the materials they need, each selecting from the surrounding elements whatever contributes to its well-being. Now, corals possess in an extraordinary degree, the power of assimilating to themselves the lime. contained in the salt water around them; and as soon as our little coral is established on a firm foundation, a lime deposit begins to form in all the walls of its body, so that its base, its partitions, and its outer wall, which in the sea-anemone remain always soft, become perfectly solid in the polyp coral, and form a frame as hard as bone.

It may naturally be asked where the lime comes from in the sea which the corals absorb in such quantities. As far as the living corals are concerned the answer is easy, for an immense deal of lime is brought down to the ocean by rivers that wear away the lime deposits through which they pass. The Mississippi, whose course lies through extensive lime regions, brings down yearly lime enough to supply all the animals living in the Gulf of Mexico. But behind this lies a question, not so easily settled, as to the origin of the extensive deposits of limestone found at the very beginning of life upon earth. This problem brings us to the threshold of astronomy; for the base of limestone is metallic in character, susceptible therefore of fusion, and may have formed a part of the materials of our earth, even in an incandescent state, when the worlds were forming. But though this investigation as to the origin of lime does not belong either to the naturalist or the geologist, its suggestion reminds us that the time has come when all the sciences and their results are so intimately connected that no one can be carried on independently of the others. Since the study of the rocks has revealed a crowded life whose records are hoarded within them, the work of the geologist and the naturalist has become one and the same; and at that border-land where the first crust of the earth was condensed out of the igneous mass of materials which formed its earliest condition, their investigation mingles with that of the astronomer, and we cannot trace the

limestone in a little coral without going back to the creation of our solar system, when the worlds that compose it were thrown off from a central mass in a gaseous condition.

When the coral has become in this way permeated with lime, all parts of the body are rigid, with the exception of the upper margin, the stomach, and the tentacles. The tentacles are soft and waving, projected or drawn in at will; they retain their flexible character through life, and decompose when the animal dies. For this reason the dried specimens of corals preserved in museums do not give us the least idea of the living corals, in which every one of the millions of beings composing such a community is crowned by a waving wreath of white or green or rose-colored tentacles.

As soon as the little coral is fairly established and solidly attached to the ground, it begins to bud. This may take place in a variety of ways, dividing at the top or budding from the base or from the sides, till the primitive animal is surrounded by a number of individuals like itself, of which it forms the nucleus, and which now begin to bud in their turn, each one surrounding itself with a numerous progeny, all remaining, however, attached to the parent. Such a community increases till its individuals are numbered by millions, and I have myself counted no less than fourteen millions of individuals in a coral mass of Porites measuring not more than twelve feet in diameter. The so-called coral heads, which make the foundation of a coral wall, and seem by their massive character and regular form especially adapted to give a strong, solid base to the whole structure, are known in our classification as the Astræans, so named on account of the little [star-shaped] pits crowded upon their surface, each one of which marks the place of a single more or less isolated individual in such a community.

Selections used by permission of Houghton, Mifflin & Company, Publishers.

223

AGATHIAS

(536-581)

GATHIAS tells us, in his 'Prooemium,' that he was born at
Myrina, Asia Minor, that his father's name was Memnonius,

and his own profession the law of the Romans and practice in courts of justice. He was born about A. D. 536, and was educated at Alexandria. In Constantinople he studied and practiced his profession, and won his surname of "Scholasticus," a title then given to a lawyer. He died, it is believed, at the age of forty-four or forty-five. He was a Christian, as he testifies in his epigrams. In the sketch of his life prefixed to his works, Niebuhr collates the friendships he himself mentions, with his fellow-poet Paulus Silentiarius, with Theodorus the decemvir, and Macedonius the ex-consul. To these men he dedicated some of his writings.

Of his works, he says in his 'Prooemium' that he wrote in his youth the 'Daphniaca,' a volume of short poems in hexameters, set off with love-tales. His 'Anthology,' or 'Cyclus,' was a collection of poems of early writers, and also compositions of his friend Paulus Silentiarius and others of his time. A number of his epigrams, preserved because they were written before or after his publication of the 'Cyclus,' have come down to us and are contained in the 'Anthologia Græca.' His principal work is his 'Historia,' which is an account of the conquest of Italy by Narses, of the first war between the Greeks and Franks, of the great earthquakes and plagues, of the war between the Greeks and Persians, and the deeds of Belisarius in his contest with the Huns, of all that was happening in the world Agathias knew between 553 and 558 A. D., while he was a young man. He tells, for instance, of the rebuilding of the great Church of St. Sophia by Justinian, and he adds:-"If any one who happens to live in some place remote from the city wishes to get a clear notion of every part, as though he were there, let him read what Paulus [Silentiarius] has composed in hexameter verse."

The history of Agathias is valuable as a chronicle. It shows that the writer had little knowledge of geography, and was not enough of a philosopher to look behind events and trace the causes from which they proceeded. He is merely a simple and honest writer, and his history is a business-like entry of facts. He dwells upon himself and his wishes with a minuteness that might seem self-conscious, but is really naif; and goes so far in his outspokenness as to say that if for the sake of a livelihood he took up another profession, his taste would have led him to devote himself to the Muses and Graces.