Excerpt from Protozooelogy There is need, furthermore, of caution in studying protozoa under such artificial conditions, for they are extremely sensitive to variations and are readily adapted to new conditions. The reactions, both morphological and physiological, of protozoa under such conditions of study require careful control. The study of protozoa, therefore, even when it is possible to apply bacteriological methods, is fundamentally different from the study of bacteria as at present carried on. The latter, dependent upon growth conditions, colony formation, reactions to media, etc., are essentially physiological and based upon the functions of the organisms. The study of protozoa, on the other hand, is essentially morphological, or based upon the structures of the protozoan cell, and involves the changes in cell structures which an individual undergoes during various phases of vitality. Hence it becomes necessary, first of all, to know the life history of the protozoon and the fundamental modifications which its protoplasm assumes. Modern protozoology, therefore, has demanded as a basis for genera and species of protozoa a knowledge of the complete life cycle, and as a basis for classification not the strue tures of the single cells, but the structures which the protoplasm may assume throughout its entire life history from fertilization to death or until the next fertilization. The present volume, finally, does not aim at being an exhaustive treatise on the protozoa; it aims, rather, to give an introduction to the study of modern protozoo'logy as seen from the author's point of view; and for numerous omissions, incomplete references, etc., he can only plead the excuse of a large subject crowded into a limited space. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.