applies not only to individuals, but to groups of individuals -for any group established with general likeness still tends to vary in relation to other groups. In our barn-yards new breeds of horses appear. The Jersey cow gets fixed as a structural form with specific color and milking qualities. This variation man assumes to control, and largely does control, creating to suit his purposes animals or plants at will. If he wants speed, he breeds for that end; if flesh, he selects in that direction; if intelligence, it is not beyond his power to secure it.

The processes pursued you understand; while the sum of the laws that he must obey is this, that any living form, whether plant or animal, follows an established heredity modified by environments. Heredity itself brings certain fixed tendencies of variation in itself to follow an established route. So we must say that the circumstances or environments, which may be placed about and brought into a range of influence upon growth at any stage, must co-operate with a determined drift in the creature itself to follow an established line of development, involving fixed and established breaks, leaps, or irregularities. All descendants, under precisely similar conditions, would be exactly alike, only that heredity itself brings in it either instability or established tendencies to vary. But, as conditions, within and without, infinitely vary, no two of any progeny are exactly alike.

We shall have occasion before we finish these lectures to consider more fully what heredity is, and shall find it to be an achievement of purpose. It is elemental "chaos" working upward into definite order on the line of aim and intent. Life never appears except as purposive and possessed of tendency; so it is that heredity is in reality the power of an idea to control environments; while the power of environments is shown in modifying the idea. Under these natural laws and conditions we work as physical and moral agents. The farmer says I must secure the right

environments, and my horses or cows, already possessed of a definable heredity, can be made to vary largely according to my desires. That is, he supplements the purpose in heredity with his own purpose and determinativeness. In my vineyard I know how to so cross a hardy Concord with a luscious but tender Hamburg as to secure a progeny involving in different degrees the qualities of both parents. My Ayrshire cow is still a cow notwithstanding her long line of ancestry bred on the Scotch hills; but she brings her modified tendencies as a cow, having lived for generations by climbing for food, and getting it by hook and by crook; for now she is still a climber and will be a climber for generations after it is needful. She will walk up-stairs to a hay-mow, get her forefeet up a leaning apple-tree; and will get a good living, keep fat, and furnish abundance of milk where another breed would starve. But those horns of hers have been well educated to wild life and the defense of her scanty bits of herbage, and they are very dangerous and will be used in a reckless way these many generations. So it is that born instinct and function vary and become established as variations. And I, if I comprehend this, will breed my Ayrshires with cattle educated and framed elsewhere; and, though I may lose somewhat of hardiness and intelligence and thrift, I will gain in the way of good

manners.

But Nature never fails to remind us that heredity is only a slowly established tendency, and that permutation is the original tendency in nature; for, if you succeed in breaking up an established order or species, you will find the most persistent effort necessary to prevent unlimited variation. Mutability can be overcome only as mind is brought to bear either within or upon an organism. The difficulty is not so much to secure a new variety or a new species as it is to establish and confirm it. Five years ago I had in my garden five varieties of beans. They were oldestablished sorts that seemed ready to reproduce their own

kinds. I cross-bred them, however, and now have from the original five varieties over three hundred varieties, differing in color, form, growth, and other characteristics. But I can not stop the variation. The tendencies that were fixed are now broken up, and the tendency to vary is established. Those which show excellencies worth preserving can not be kept as they are, without great difficulty. You may even expect some astonishing leaps and freaks, or reversions to old ancestry, in any such experiment.

But heredity once established becomes a law-an inherent determinative force; it is plant will or elemental will. This, however subject to environments of a new order, retains a large share of its grip. Wheat remains wheat whether carried to a warm or a cold climate; but in one place it is spring wheat, in another it becomes winter wheat. Your Northern Spy, best in New York during March or April, if grown in Missouri is a Fall apple. A peach is still a peach, grown on sandy or on clay soil, but you soon discover that the soil very decidedly affects the size and the quality of your fruit. You are, however, puzzled, when you come to classify your fruits, to find that peaches, pears, apples, plums, apricots, and even blackberries and strawberries, are all members of the same general family. Did they come from one stock originally? The believer in the production of all forms by evolution answers that they did. His opponent refuses to allow that variation can go beyond the line of species. This objection. to variation has lost its force, but in a general statement of the question it needs consideration. Nothing is more certain than that the force that lies in heredity itself drives across specific lines, giving us out of one stock or genus several absolute species. The almond, peach, and nectarine, all species well defined, are purely breaks or "sports " of one ancestor. Hybridization accomplishes results of the same sort. That is a propulsion within, a force involved in heredity, or a purposive influence from without,

can break through the dividing walls between species. All acknowledged authorities confess species to be but an imaginary line, indicating extremes of variation between groups that vary less within their own limits. Varieties indicate weak life currents; species, strong life currents. Drift in nature is not easily overcome. What we mean by species is only a strong tendency in a group in a certain direction, and accumulation of life power to do and be a certain thing. It is not easy to overcome this; and if overcome, the tendency is to sterility of the issue. The parents do not harmoniously blend in aim and purpose. But the known cases of fertile hybrids show that there is no law in this direction that can not be overcome. Sterility depends not on specific differences, but on larger facts, such as constitutional dissimilarity, which is the sum of all multifold causes involved in the process of integrating. It is even quite difficult to cross certain varieties within a species. To make the point clear by a familiar illustration : in my experiments with beans it is far more difficult to secure a cross of the Lima with other common beans than to secure a cross in other directions, simply because the Lima is highly specialized, and its heredity has secured a greater degree of inflexibility. The domestic cattle of Europe are the fertile progeny of three well-defined species belonging to the Diluvial era. These species have perished into one that survives. The truth seems to be that specific types tend to vary precisely as other types vary, only in less degree.

Evolution is the hypothesis that asserts that we have in these laws of descent and variation a complete explanation of all that has occurred since "the beginning" of life. We may reduce the general hypothesis to the following formal terms: 1. Life began on our globe as a simple protoplasmic cell, or the simpler antecedent of such a cell, from which, in long periods of time, to us practically infinite, have been evolved all organic and functional changes. 2. Each individual and each group of plants

or animals inherits a modifiable tendency and character. 3. The variations in any plant or animal may become fixed and capable of being inherited, thus giving rise to varieties, and, in time, to species. 4. The destruction of many varieties and the survival of some, is determined in general terms as the survival of the fittest, which does not mean the survival of the best, either physically or morally, but of those best fitted to protect themselves in the struggle for existence. 5. The struggle for ex

istence goes on at all times and everywhere as an essential process of natural forces involving desires to be gratified. Hunger lies at the bottom of all living, and underlies all structural changes. 6. Through all changes and all generations one unceasing purpose runs-a purpose to progress from the simple to the complex, from the physical to the ethical, and so it is that the monad climbs to man by the power of sentient will.

Evolution thus gives us, in the place of an extra-natural Creator, a power in Nature itself to solve the puzzle which met us at the outset-namely, an enormous multiplicity of varieties and species of animals and plants, all correlated and classifiable in groups and kingdoms of groups, the kingdoms themselves being interactive and co-operative. Linnæus said, "There are as many different species as there were different forms created in the beginning by the Infinite Being." The evolutionist answers, Species cross as varieties vary, only with more bias to overcome, and they do so by determinable methods, all of which lie within Nature. Darwin only went so far as to say, "There is grandeur in this view of life, with its several powers originally breathed by the Creator into a few forms or one; while from so simple a beginning endless forms, most beautiful and most wonderful, have been and are being evolved." Mr. Darwin, in such a passage, considers the processes of life, and not its origin, which he presupposes to be the fiat of a creator. Evolutionists of this day will, however, not