The world is simpler than we think. The modes and processes of things widely dissimilar are more likely to be identical than we suspect. There are homologies where we see apparent contradiction. There is but one protoplasm for animal and vegetable. A little more or less heat makes the gaseous, makes the liquid, makes the solid. Lava crystallizes or freezes at a high temperature; water, at a low one; mercury, at a still lower. Charcoal and the diamond are one; the same law of gravitation which makes the cloud float makes the rain fall. The law that spheres a tear spheres a globe. These facts warrant us in looking for real homologies, vital correspondences, in nature. Only such correspondences give logical and scientific value to analogy. If the likeness means identity of law, or is the same principle in another disguise, then it is an instrument of truth. We might expect to find many analogies between air and water, the atmosphere being but a finer ocean; also between ice and water, and between ice and the stratified rocks. If water flows, then will ice flow; if ice bends, then will the rocky strata bend. If cross fertilization is good in the vegetable world, we should expect to find it good in the animal world. There is thought to be a strict analogy between the succession of plants in different months of the year and the prevalence of different diseases at different seasons. The germ theory of disease gives force to the comparison. The different species of germs no doubt find some periods of the year more favorable to their development than others. If on this planet men walk about while trees are rooted to the ground, we may reasonably expect that the same is true--provided that on them there are men and trees--of all other planets. If the law of variation, and the survival of the fittest, are the laws of one species, then they will prove to be the laws of all. The bud is a kind of seed; the fruit is a kind of leaf. High culture has the same effect upon man and animals that it has upon plants,--it lessens the powers of reproduction. The lowest organisms multiply by myriads; the higher barely keep from retrograding. A wild apple is full of seeds; in a choice pippin the seeds are largely abortive. Indeed, all weeds and parasites seem bent on filling the world with their progeny, while the higher forms fall off and tend to extinction. Such agreements and correspondences point to identity of law. The analogy is vital.