PROBABILITY, THE FOUNDATION OF EUGENICS.* The request so honourable to myself, to be the Herbert Spencer lecturer of this year, aroused a multitude of vivid recollec¬ tions. Spencer’s strong personality, his complete devotion to a self-imposed and life-long task, together with rare gleams of tenderness visible amidst a wilderness of abstract thought, have left a unique impression on my mind that years fail to weaken. I do not propose to speak of his writings ; they have been fully commented on else¬ where, but I desire to acknowledge my personal debt to him, which is large. It lies in what I gained through his readiness to discuss any ideas I happened to be full of at the time, with quick sympathy and keen criticism. It was his custom for many after¬ noons to spend an hour or two of rest in the old smoking room of the Athenaeum Club, strolling into an adjoining compartment for a game of billiards when the table was free. Day after day on those afternoons I enjoyed brief talks with him, which were bften of •The Herbert Spencer Lecture delivered before the University at Oxford, June 5th, 1907.