The old problem of Nature _versus_ nurture that meets us in studying the life history of any organism becomes especially interesting in dealing with the biography of men of eminence. Are their achievements the inevitable expression of the natural forces innate in them at birth, or the product of environmental influences, or some resultant of these two factors? And how much may we in each case assign to one factor or to the other? These difficult questions naturally suggest themselves in glancing at the life of the subject of this sketch. Like so many men who have won prominence in comparatively new countries, he seemed, in an environment that had no apparent relation to his future, to grow from innate tendencies toward something not suggested by the circumstances about him, even to grow in opposition to the molding influences of these, and to conquer them. Later, however, we find him surrounded by influences that made a particular mode of self-expression easy, if they may not be said to have forced such expression. It was then that the casual observer might say that the circumstances made the man; yet, looking backward, we can trace the initiative in the man that led him into the congenial environment. A selection of proper environment to express Nature has been rightly claimed as a potent factor in all organic life; nurture, then, comes as a secondary power to mold, or rather to translate, the inherent power. WILLIAM KEITH BROOKS, the second son of Oliver Allen Brooks and Eleanora Bradbury, daughter of the Rev. Phineas Kingsley, was born in Cleveland, Ohio, in 1848. In 1877 he married Amelia Katherine, daughter of Edward T. Schultz and Susan Rebecca, daughter of David L. Martin. He has two children. Brooks grew up amid the stimulating influences of a relatively new country, where freedom of development was not so sharply restricted but that all paths of life seemed equally open to one who would work. As a boy he was not one of those precocious naturalists of the common sort whose collecting instincts find expression in the hoarding of dead animals or plants rather than the neater postage stamp; names and authorities, classes and species, neatly arranged mummies, were not his delight. At first there seemed no sign that zoölogy would claim him as a most ardent admirer. Yet he was fond of live things and their ways, and introduced into his home that most delightful microcosm, the fresh-water aquarium (so much neglected in this country), in which he could observe at ease the habits and slow changes of living things when their native haunts were not accessible. Such early interest in the essential wonders of livingness rather than in man's artificial classification of phenomena was thus prophetic of much of his later originality of thought and view. He has never forgotten how much he owes to the instruction of the earnest and broad-minded teachers in the public schools of Cleveland.