The acceptance of an invitation to outline for you in a few minutes the recent advances in cytology places me between two hazards characteristic of such a situation. On one hand is the danger of making statements so general and obvious that they would be devoid of new meaning and therefore wasteful of your time, and on the other is the risk of presenting an arid recital of bare facts equally unkind to your patience. The difficulty increases when one inclines toward a definition of cytology broad enough to include any work in which the cell is more or less directly studied with scientific method, no matter what the special avenue of approach; and when one regards as advances not simply the establishment of new facts or the attainment of certain temporary goals, but also the consideration of old facts from new points of view, the recognition of errors, the invention or adaptation of new methods, the formulation of new and useful provisional hypotheses, the correlation of neighboring fields of research, and the confident entry upon new paths of endeavor. Neither in generalities nor in particulars alone can recent cytological progress be represented. I shall therefore follow a somewhat ill-defined middle course by limiting my account to a very few of the developments which cytologists have recently witnessed in their field, with some indication of their reasons for considering them of sufficient significance to be brought before you on this occasion. Protoplasm. I can think of no problem of more fundamental importance to cytology, and to all biology, than that of the nature of the physical basis of life. After the masterly addresses of Professor Harper at Pittsburgh and Professor Wilson at Boston I feel that comparatively little remains for me to say on this subject, but it may not be superfluous to emphasize anew the impetus which the conception of protoplasm as a colloidal system has given to all types of cell study. In the first place, it has encouraged a more thoroughgoing investigation of the cell in the living state. This has involved the devising of ingenious methods by which we have already been able to remove many misconceptions originally growing out of the too-exclusive use of fixed material. Again, by furnishing us with a new and suggestive theoretical basis of interpretation for the data obtained from morphological and physiological cell studies, it has aided us in finding plausible partial explanations for a variety of puzzling phenomena, among which we may mention cytokinesis,