If we are right in this matter, and we certainly are nearly right, variation must take place for the most part in the germ. These variations may not show until the animal has grown up, but they must have taken place among the determinants in the germ cell or they would not reappear in subsequent generations. There is another process by which new variations may arise and which is more easily understood. It is the method of double parentage. The Barred Plymouth Rock chicken had its origin in such a double ancestry. The one parent was a Black Java whose color has disappeared entirely in the cross, but whose single comb with its few large points comes out clearly in the newly produced fowl. The other parent was a Barred Dominique. It is to this parent that the Plymouth Rock owes the interesting cross markings on its feathers. The comb on the head of the Barred Dominique is of the type known as the rose-comb, having many rows of slight projections. This has completely disappeared from the Plymouth Rock fowls. I am told that the skilled chicken fancier can tell, concerning many points in this fowl, to which of the crossed ancestors each quality is due. To a certain extent it is undoubtedly true that here we have the secret of the origin of many of those interesting people whom we are pleased to call geniuses. They may not possess any qualities not clearly discernible in various of their near ancestors, but in them we find what we, for the lack of a better understanding, call chance combination in one individual of the finer qualities of many ancestors, and this individual is so placed in life as to have these qualities developed and strengthened. Charles Darwin, humanly speaking, may be accounted for as the happy combination of a double heredity and a favorable environment. He inherited the scientific inclinations of his grandfather, Erasmus Darwin, and the patient, sturdy honesty of his other grandfather, Josiah Wedgwood. These developed under the stimulus of the long five-year voyage, face to face with the world of nature. This happy complex produced the master biologist. To believe that he came about purely by chance requires a great stretch of the imagination. "There's a divinity that shapes our ends." We have endeavored to make clear two of the basal ideas underlying evolution. One of these is responsible for the continued production of animals or plants of the same kind, preventing the world from becoming a wild kaleidoscopic and fantastic dream. Heredity is the conservative force of nature. The other idea underlies the development of new departures which keep the world from being a dull, dead, unending repetition of the same monotonous material. Variation is the progressive tendency in nature.