A BY-LAW of the National Academy of Sciences (XVIII.) makes it the duty of the Secretaries to prepare an Annual, and to publish the same on the first day of each year. As but one meeting, that for organization, was held in 1863, the Secretaries were excused from the duty during that year, and the Annual now presented is intended to cover the whole period from the organization of the Academy in April, 1863, to January 1st, 1865. WOLCOTT GIBBS. LOUIS AGASSIZ. CONTENTS. PAGE 10 II. LETTER OF THE HON. HENRY WILSON, MARCH 5, 1863 III. LETTER OF THE HON. HENRY WILSON, MARCH 18, 1863 IV. ADDRESS OF HON. HENRY WILSON, DELIVERED AT THE OPENING OF THE FIRST SESSION OF THE ACADEMY, V. CONSTITUTION AND BY-LAWS OF THE ACADEMY, AS ADOPT- |