But it is not only ideas that have changed within the last two decades; methods of study have undergone an even greater revolution. De Vries, at almost the same time he discovered mutation, rediscovered the fact that heredity was by no means so mysterious and erratic as it had been generally thought. Animals and plants, he discovered, possessed many characters which behaved in very definite ways when two varieties were crossed, and that the characters of an organism could be determined largely by the interbreeding of its ancestors. Thus arose the science of _genetics_, which seeks to find out the numerous factors underlying the various phenomena of heredity. And since heredity is the base of all evolution, genetics has for its ultimate aim the determination of the causes of that great process which is responsible for the existence of whatever animals and plants inhabit and have inhabited the earth. The geneticist is the most modern of evolutionists; he is not satisfied with finding out what has taken place in the past; he sets out to make evolution, or tiny portions of it, take place within his own laboratories and greenhouses. * * * * * Today, despite the assertions of a few of its opponents, the theory of organic evolution is more thoroughly alive than it has ever been before. Paleontologists are studying their fossil shells and corals and bones in order to find out what has taken place during the millions upon millions of years during which living things have inhabited our planet. Anatomists are studying the bodies of modern animals, from the simplest to the highest, to determine their relationships one to the other; embryologists are tracing out the evolution of the individual in his life before birth. The geneticists are breeding plants, rabbits, mice, fishes, flies, potato bugs so that they may discover what evolution is doing today. Everywhere men are studying, comparing, experimenting. Their purpose is not to discover whether or not evolution is a fact; on that point they have long ago been satisfied. They are trying to find out how it operates and what forms it has produced; how differences arise among organisms, and what are their effects, and by what means they are passed from one generation to another until they become part and parcel of the inheritance, thereby establishing a new species. FOOTNOTES: [1] Modified after Zeller and Osborn. [2] Osborn, “From the Greeks to Darwin,” p. 86. [3] This claim has at various times been disputed; Osborn, however, accepts it without question. [4] “From the Greeks to Darwin,” pp. 101-102. [5] Quoted by Osborn, with the comment: “As Haeckel observes, Darwin rose up as Kant’s Newton.”