OF THE AMERICAN ACADEMY OF ARTS AND SCIENCES. NEW SERIES. VOL. XII. WHOLE SERIES. VOL. XX. FROM MAY, 1884, TO MAY, 1885. SELECTED FROM THE RECORDS. BOSTON: UNIVERSITY PRESS: JOHN WILSON AND SON. CONTENTS. PAGE 1 V. The External Morphology of the Leech. By C. O. WHITMAN VII. Descriptions of New Species of Cambarus; to which is added a Synonymical List of the known Species of Cambarus and VIII. A Method of Measuring the Absolute Sensitiveness of Photo- |