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past reveal; and, as we have seen, the procession of life was necessary as a prelude to the life now existing, being the strong stem which bears its weight of flower and fruit. Not only so, but it would appear that as the life of an individual is a succession of changes, and perfect equilibrium would be death, so the life of a species is only maintained by the ever-varying action of outward forces, and an absolutely uniform species, having all its members exposed to identical influences, would cease to exist. The changing conditions which ultimately lead to the formation of new species are a primary necessity of continued life in any form.

When outward changes take place too rapidly species are sometimes extinguished; and therefore we ought to admire the arrangement which makes climatal and geological changes proceed slowly, so that slight variations in living things may suffice, and no wrench be given to their organization. It is imaginable that the outward changes should be in the way of constant small oscillations, tending to undo one day what they did the day before, and possibly in these circumstances species would remain nearly uniform; but the continued onward march of "conditions," carrying living things with them by adding up their variations in definite directions, is surely grander. It is conceivable that the conditions should show great variations within small areas, modifying every individual differently, instead of being nearly uniform for large portions of the earth's surface; and then there would really be force in the objection made against Natural Selection, that unless many individuals were similarly modified simultaneously the new forms would soon be swallowed up by commingling with the old. It may be observed also, that but for changing

geological and meteorological conditions the world would never have presented the varied beauty which it exhibits the mountain, the river, the lake, the valley, headlands and islands, crags and cliffs and

caves.

A whole chapter might be inserted in this place showing the wonderful development of organisms through the action of outward forces, including heat and light, soil, water, air, food taken into the stomach, and the mutual action of the organs and parts of a body on one another. The development of each individual organ, including the complicated apparatus of the human ear, and the almost perfect instrument of the human eye, would only seem the more admirable when the stages and means of their progress were made manifest. But time fails us.

In the effects of Use and Disuse.—Among the external conditions affecting an organism are those stimuli which lead to an increased use of any organ. The fact that unused organs degenerate and become rudimentary has its converse in the circumstance, that when organs are much exercised (if not over wrought) they become stronger. The blacksmith's arm is a familiar instance, to which may be added the fact, that bones subject to greater strains acquire greater massiveness: it is well known that variations in the muscular strains call forth by reaction variations in the strength of the bones. The great and inherited development of the udders in cows and goats in countries where they are habitually milked, in comparison with the state of these organs in other countries, is another instance of the effect of use.

What arrangement could be simpler or more beautiful than that the increased strain to which an organ is

subject to-day, should increase its power to resist strain to-morrow-that the demand should create the supply in the very region where the demand is made, and within reasonable limits, to the extent to which it is made? It is like the fire in Bunyan's house of the Interpreter, whose blaze increases with every effort to put it out, because there is a secret supply of oil from behind, more than compensating for the stream of water in front. And observe, that the increment of strength would be useless unless the circumstances of a creature's environment were kept moderately uniform for some length of time, so that the same demand on the same organ should be made again and again.

The material for the strengthening of a muscle or a bone must, however, come from somewhere; and as the organism is a whole, and nature has a disposition to economise, a certain balance is sometimes observed, as though the new supply of nutriment were merely a transfer from some other part of the body. In our poultry, a large tuft of feathers on the head is generally accompanied by a diminished comb, and a large beard by diminished wattles; and perhaps the entire absence of the oil gland in fantail pigeons may be connected with the great development of their tails. The difficulty of finding very many plain cases is perhaps an indication that this is not nature's usual method; and that when she resorts to it, it is because there is not at the moment a sufficient supply of food finding its way to the organism from without, or because the parts drawn upon can bear the drain, not being themselves of much use to the individual. If this be so, we may find an analogy in the diversion of the China expedition under Lord Elgin, to meet the sudden and pressing demands of the Indian

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mutiny by this means India was saved, and by means of compensation of growth nature saves the body.

Evolution of living matter.-Oxygen, hydrogen, carbon, and nitrogen, are all lifeless bodies. Oxygen and hydrogen, by their chemical union, form water; oxygen and carbon combined in certain proportions constitute carbonic acid; hydrogen and nitrogen by uniting give rise to ammonia: but these compounds are as lifeless as the elementary bodies of which they are composed. When, however, these three compound bodies are brought under the influence of living protoplasm, they become living protoplasm themselves! How this comes about is quite unintelligible to us; the marvel of life is not understood, nor the marvel that living matter should be able to make other living matter. Not all the chemists of Germany can so put together the elements as to make a speck of protoplasm: and even if they should some day succeed in doing so, the natural wonder will not be diminished-man will be treading the track of the Creator," thinking His thoughts after Him," but it will remain the fact, that what the 19th century with difficulty accomplished was thought and done with ease in the beginning.

Heredity. The marvel is multiplied a million fold when animals high in the scale of being produce offspring resembling themselves. The one end to which, in all living beings, the formative impulse is tendingthe one scheme which the Archæus of the old speculators strives to carry out, seems to be to mould the offspring into the likeness of the parent. It is the first great law of reproduction, that the offspring should resemble its parent or parents more closely than anything else; and the rule is so seldom departed from, that

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the human child which did not resemble either the paternal or the maternal side of the house would be regarded as a kind of monster. The marvel is none the less because it occurs often; and should science one day show us the reason of its occurrence, the fact will be what it is at present, and the process may call for additional admiration.

At present the laws governing inheritance are quite unknown. No one can say why the child resembles his parents; no one can say why a peculiarity in an individual is sometimes inherited and sometimes not, why the child often reverts in certain characters to its grandfather or grandmother, or some more remote ancestor; nor why a peculiarity is often transmitted from one sex to both sexes, or to one sex alone-more commonly, but not exclusively, to the like sex, the mother's peculiarity to the girl, the father's to the boy. When these things come to be understood, the wisdom of the Creator will probably receive new illustration.

Variation. Through geological and other changes the circumstances of a creature's environment are continually being altered, and yet the condition of existence is, that an organism shall be adjusted to its environment, the inward forces balancing the outward forces. Therefore, given the external changes as a fact, and living things must vary, or else they will die. The arrangement is beautiful from whichever side we view it: if it is good that creatures should live, and change is necessary to life, and variations in the environment are fitted to produce change in the organism, everything is admirable; or if cosmical and geological changes are a matter of necessity, and organisms must be adjusted to them, and