Does anyone imagine that the careful selection of seed by the gardener is constantly effecting an improvement in his stock commensurate with the vigour of his work? Such an impression would be a great mistake. The changes which take place in our cultivated plants are more in the nature of oscillation than of systematic development.

Darwin says in The Origin of Species, that almost all our cultivated vegetables have been "greatly improved in many ways within a recent period." This is doubtless true, and the work still continues; but it is not safe to assume that progress is constantly in the right direction merely because improved varieties are continually being introduced. Sometimes after many improved strains have been raised the net result is one step back. The law of deterioration, or it may be the law of reversion is at work, and frequently it proves stronger than our efforts.

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An instance of this was brought before us only a few days before the first notes of this chapter were written. A special strain of celery selected a few years earlier had completely lost its superiority. It was the finest celery we have ever seen, and great efforts were made to preserve its characteristics. It appears, however, that either our selection was not rigorous enough, or else such excellence was stretching the elastic too far and the strain could not be maintained.

Perhaps the potato furnishes a still better illustration of reversion or deterioration. There can be no reasonable doubt that during the last half of the nineteenth century, in spite of continuous efforts to raise improved varieties of potatoes, the net result was a long step back. The potatoes grown during the latter half of this period was not as vigorous and nothing like as free from disease as their parents of fifty years earlier. We need not rely upon the memories of old men for this opinion. A comparison of prices yields the same conclusion. Sixty or seventy years ago wheat was so dear that poor people could hardly afford to buy bread. They were helped to live by the fact that potatoes were much cheaper after the rate. As farmers naturally grow the crops which pay them best, there is only one conclusion to draw from this fact. The potatoes in those days were more vigorous and produced a better crop. This is all the more remarkable in view of the fact that great efforts have been made to effect improvements.

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The improvements have been real in a sense, but the law of deterioration has been stronger. The fact that a variety of potato gets "played out," in course of time is, we suppose, too well known to need any argument. The constant efforts of the raiser of new varieties is to produce something as good as, or, if possible, better than the old variety was when it was first introduced. It appears, however, that in this case the law of declension has proved too strong. Some real improvements have been effected during the last few years, and it may be that some time a potato will be introduced as vigorous, and as free from disease as the parents were previous to the year 1845. If this ideal is ever reached it will be by the application of man's intelligence, not by chance, and by a selection far more vigorous and more persistent than natural selection can ever be.

In this connection we must refer to a very practical matter. The majority of our plants are so prodigal in the production of seed that it is easy for the gardener or farmer to save seed for next year's crops. A very few plants would supply all the seed required. Very often, however, the practical man finds that it pays him better to buy the seed for another year, even at relatively high prices. The large growers have great facilities for making proper selection and the most rigorous selection is necessary if the high level of our cultivated plants is to be maintained. Even the best and most skilful raisers are continually bringing out new varieties which prove failures. It

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is beyond question a fact that the more we improve a plant the harder it Is to effect further improvement, or even to sustain the level already reached.

Surely the very fact that there is such a law of reversion is indicative of creation. The illustration of the elastic well fits the case. A piece of elastic has a natural shape, but it can be stretched considerably. The nearer we approach to the vaguely defined limits of its capacity the harder it is to stretch it farther. If plants and animals had all evolved from the simplest of forms which in turn had come into existence by chance; every stage in the long line of development would be equally natural. We could not reasonably expect any more tendency to revert than in the case of a plastic lump of putty. Why should the law of reversion become stronger as we proceed in our work of selection unless it is that the products of Nature are really the creations of God.

To summarise under this heading we may give a practical answer to the question put by the great naturalist. Darwin recognised the fact of reversion, but asked why it should prevail against natural selection if man had succeeded in overcoming it?

We will take the case of a plant of any prolific family, and note the difference between artificial selection and natural selection. A single plant might produce a thousand seeds. The gardener makes the most rigorous selection in order to secure the very best. The chosen plants are isolated,

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guarded from enemies and treated with the utmost care. The seeds are all sown in the best of ground. The young plants as they appear are pricked out so many inches apart, and again most carefully tended. They are guarded in every way from the struggle for existence. If only three plants out of ten thousand come true to the quality that the gardener is selecting, the nine thousand nine hundred and ninety-seven are ruthlessly cut down, and the three are isolated and cared for in every possible way. This tremendous force of selection goes on for generations, all the energy of the gardener being applied to the work, and the effort always in the same direction. Even then the most skilful raiser is often beaten and the plants revert to the parental character.

What is there in Nature to present the slightest analogy to this? In some instances there is so much destruction that in spite of a yield of a thousandfold there is no increase in the number of plants; that means a destruction of nine hundred and ninety-nine potential plants and the preservation of only one. It may be said, "What an opportunity for selection here." We answer, "Yes; if there is someone here to select the one seed out of a thousand.," That is what the gardener does when he raises a new and distinct variety, but is anyone foolish enough to. suppose that under natural conditions the work of elimination is so regulated? Hundreds of the seeds are devoured by animals, birds; or insects, and if there is any selection it is simply to destroy the best. Hundreds more will

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fall by chance in places where they cannot possibly grow. Many may cling to the fur of animals, eventually to be thrown off into the water, or into dark caves where germination is impossible. Of the few which fall into a soil in which they can grow some will not go beyond the production of the first tender shoot, for it will be eaten off by a hungry enemy, the life of the plant thus being stopped at the outset. In all this there is no selection whatever, but simply the complex play of many chances.

The first plants which escape these chance destructions will almost certainly ripen their seed, struggle how they may, and there will be the inevitable cross fertilization between those which vary and those which remain true to type, or between plants whose variations run in different directions. What can be accomplished by the struggle for existence between these few specimens? What can possibly follow but a measure of degradation commensurate with the severity of the struggle? That is always the result.

The gardener with a consistent aim selects the one plant in a thousand, and again the one in a thousand of the next generation. He guards against cross fertilization as much as possible. He takes care that all the seeds from his chosen plant shall show their quality, and he ruthlessly roots out all that fail to please him. Even then the law of reversion often beats him.

Nature with no aim at all, allows the great majority of the seeds to be destroyed, or to be placed

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where they cannot germinate. Then she allows indiscriminate cross fertilisation between the few plants that chance to grow. With the next generation the process is repeated, with a thousand chances to one against the selection of the seed which would most fully carry forward the special peculiarities of the parent.

Darwin asks why should the law of reversion prevail against natural selection if man can sometimes overcome it?

Well, we think that if ever a question has been answered, assuredly we have answered this.