two oldest land-snails-one is elongated, the other rounded. In this age or earlier, they emerged from the waters, moved on the land, and breathed air. The oldest known fossil butterfly has relationship with some living butterflies of tropical America. In the Neozoic ages appear nearly all the order of insects. They are of later origin, as Scripture declares, than the moving things of the waters. There is a scientific hypothesis that their progenitors were crustacea. Strange that Spirit can so infuse with life, blend and interknit the low with majesty sublime!

The division and development of life appear to have been in this order-Plants reduced special elements, existing in gaseous and watery combination, to a solid form. Animals, deriving their forces directly or indirectly from plants, carried the transformation a step further. The structural and functional motions of every organism being an advance from the motions of molecules to those of compound molecules, and from these to masses. For example: sea-snails are united by many intermediate forms, and seem to have been the progenitors of fresh-water and land snails. The celebrated and various snails of the Stuben Valley, near Steinheim, Würtemberg, whose snow-white shells constitute more than half the mass of the Tertiary limestone hills, exceed twenty different species; but the extreme forms are linked by so many intermediate, lying regularly above and beside one another, that their pedigree is easily traced. God stands for the cohesion of all, yet all separating.

Historical succession is generally indicated: (1) in the palæontological history of organisms, furnished by fossils in their adaptation to those various changes in the earth, of which increase or decrease of temperature was the master fact affecting climate, food, land, and sea level; (2) in the history of individual organisms; (3) in the comparative anatomy of kindred organisms. These three main facts prove that a marvellous process of adaptation has been in operation from the very beginning. The Nummulites, whose shells, the size of a lentil, form nearly whole mountains in the Alpine system of Europe, and deposit thousands of feet in thickness in Africa and Asia, possess a house with many little chambers artistically ordered. The Polythalamia have shell-chambers wound round one another in a spiral line and great variety of exquisite forms. These little palaces of beauty, regular

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structure, elegant execution, are the product of a slimy, formless, living mass; and various, as their products, are the builders themselves. The differences, imperceptible in their chemical composition and physical construction, are brought plainly into view by the variety of their constructed habitations of minutest and most splendid architecture.

The chasm between creeping thing of the land and swarming thing of the sea is bridged by intermediate forms; so, between fish and animal of the land, come those amphibia of which ancient days afforded gigantic examples. Are we to conclude that the land was colonised from the water? We may smile at those who assert every foot comes from a fin, and fish developed lungs by gaping; but as twice a day, in the rise and fall of the tide, some plants and animals have a twofold kind of life; it is easy to think of an advance of life from the sea to possess the land. Heredity from the water might be so acted upon through adaptation by land, that at last animals could wholly forsake one for the other. The mud-fish is an example of transition into amphibia, and the tailed forms of amphibia are the most ancient. Tritons are amphibious animals, akin to frogs; and, like them, in an early stage, possess gills, by means of which they live and breathe the air that is dissolved in the water. At a later stage, like frogs, they leave the water, lose their gills, and are able to breathe with their lungs; but if, by being shut up in a tank, they cannot leave the water, they retain their gills. The gilled salamander, Axolotl (Siredon pisciformis), generally remains all its life in the water; but at the Zoological Garden, in Paris, not long ago, a small number crept out of the water, from the many hundreds of their fellows, lost their gills, and became gill-less salamanders-breathing only through their lungs. Salt-water crustacea and fish also live in the great fresh-water lakes of the world. Things soft as breath, with gentle wave as by the hand, may advance to life upward tending.

Adaptation to circumstances works structural changes in the properties of already formed parts; but, during any assigned time, these changes fall within narrow limits; and soon as the normal state is re-established, the organ and organism fall back to their original condition. Structure, handed down by heredity, is liable to variations; in part by the individual, in part by involved influences producing

functional adaptations; but only power from without, acting within, accounts for the continual introduction throughout all geological time of new forms. As to artificial acquirements, plants and animals when neglected relapse to their original wild forms; and mutilations of the body-though continued from generation to generation, as nose and ear piercings, misshapings of the foot-as among the Chinese, and circumcision-as by the Jews, are not transmitted. However much lower forms of life mingle; and outward grades of fish and amphibia, marsupial and mammal, approach one another; distinct provinces of marine and terrestrial life are maintained.

The marsupial form, akin to reptile and amphibian, preceded the other mammalia in time. Of the Mesozoic species all are marsupial, small, of low grade, and allied to the monotremata in their lowest structures; but not lower than some now existing. Their low position may be associated with the habit of limiting the exercise of active-life faculties to the period of night's obscurity. The mother nurses her young in a tegumentary pouch, where they remain suspended to the teats, and are safely carried for a period nearly answering to that of uterine life in the higher mammals. Where great want of water exists; and, in dry seasons, rivers are converted into pools few and far between; in such a climate, at such a time, an ordinary non-marsupial animal like the wild cat or fox, having deposited her young, would travel far to quench her thirst. "Before she could return her blind and helpless litter would have perished. By the marsupial modification the mother is enabled to carry her offspring with her in the long migrations necessitated by the scarcity of water." Mr. Owen adds-"These correlated modifications of maternal and fœtal structures, designed with special reference to the peculiar conditions of both mother and offspring, afford, as it seems to me, irrefragable evidence of creative foresight." A difficulty attends this theory: the pouch is not possessed by all marsupials.

The great class of mammals had a small beginning, and made little or no advance during the vast Mesozoic time. In the Neozoic time existed that higher group which now has pre-eminence. Animals related to tapirs, bears, racoons,

1 "Classification and Geographical Distribution of the Mammalia: " Richard Owen, F.R.S.

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are among the oldest. The Miocene was the culminating age of mammalia: they were then largest and most numerous. The Deinothere was as much larger than our elephant as the elephant exceeds an ox; the skull, including snout, was five or six feet long; two large tusks grew out of the end of the lower jaw and pointed downwards. The most ancient beasts of prey are the feline, then the canidæ, latest the ursidæ. Relics of their predecessors we do not possess. The beast of the earth and cattle are the freely roving vegetable and flesh eating wild animals of the land, creatures of marsh, field, forest, plain. The Eocene and Miocene strata of North America are crowded with carnivora, ruminantia, pachydermata, rodentia, and non-ruminating creatures of the horse, rhinoceros, pig, tribes.

Heredity, or inheritance of the parents' nature, seems to be the natural cause of stability; and Adaptation one of the causes of modification or change in organisms. Structure and function being exposed to countless actions and reactions, from generation to generation, of ever-varying circumstances, the wonder is that we have not greater varieties, and that they are not mingled in utter confusion. In species, animal or vegetable, the individuals are never quite alike; and in every species, even in every individual, there is tendency to produce varieties. Some unknown energy sets bounds to these changes; and we are amazed that the simple egg-cell of the maternal organism, and a single paternal sperm-thread, transfer to the young the minutest bodily and mental peculiarities of both parents. The germ from which most mammals are produced is the 120th part of an inch in diameter, the same size as in man.

Doubtless, we may say of life-vires acquirit eundo. The original forms of it, whether few or many, were capable of development, and received it. Every new natural principle was to the preceding as a miracle, the animal a miracle to the vegetable, and man a miracle to the beast of the field. We have a right to infer that there is a law which provides for the origination of species, de novo, which is called into action by conditions and in a manner wholly unknown. Life did not flow in an organic fixed circle; some forms were retarded; and other forms ascended in many lines of development. Every species seems to come into being at a certain definite time, and to disappear at another definite

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time; though there are few, if indeed any instances, in which we can safely fix the time for entrance or exit. This creating of new things is our general notion of miracle; foretelling the new is our general idea of prophecy. All past variety of growth and development of power were figures of future advance, or allegory of forms to come; every low grade reappearing in the higher, as subservient and supporting substance. On natural life is grafted intellectual life; on intellectual, the spiritual and moral; on spiritual and moral, future life. Life, ascending in many various paths, is everywhere subjected to spirit; and life with spirit in turn, subject and connect matter. The crystallographer connects imponderable forces and polarity; the coarse or outside substance becoming the precipitate of inner and finer formations. There are worlds within worlds; infinity contains space, space comprehends matter, matter embraces life, life enfolds intelligence, intelligence is quickened by Divine Spirit. Matter and its forms, life and its forces, are mysteries, our mind and speech expounding them are mysteries, that solution is surest and simplest which ascribes them to the power of God.

Life-forms are classed according to their differences in structure. Heredity tends to conservation; and power of Adaptation by circumstances to circumstances, tends to variety. Likeness preserves identity of species, unlikeness tends to variety. Sometimes variety arises in full force, per saltum; but in every case there are determining causes, external, internal, or both. A variety which approaches the nature of a monstrosity strives, Calibanlike, to reproduce itself; much more does the better fitted maintain the struggle for existence. Causes, acting through long ages of time, fashioned from pre-existing life-forms most of the varieties of life now on our globe; but there has been some introduction of new forms apart from preexistent allied types;1 the weaker, perishing; those excelling and best fitted to conditions, surviving. As a rule, animals of lowest and simplest organisation have the longest range of time; minute dimension is also in favour of their continuance. Large and highly organised animals, though long lived as individuals, rarely live long specifically.

1 For examples, see H, Alleyne Nicholson's "Life-History of the Earth," p. 373.