This translation from the second German edition of an exceedingly fine book presents a study of submicroscopic morphology. The author correlates the data available on submicroscopic structure of protoplasm with known chemical structures and phenomena and their inherent physical properties. The methods, technics and instruments used in carrying out such investigations are explained in detail; at the same time the limits of practical use for the methods used are stressed. The text is organized into three sections: fundamentals of submicroscopic morphology, which includes a discussion on the organization of sols, principles of structure of ions, atoms and molecules, structure of gels, and studies in gels; fine structure of the protoplasm, which includes discussions on cytoplasm, nucleus, chloroplasts and erythrocytes, and fine structure of protoplasmic derivatives, such as horny substances, muscle fibers, myelin sheath of the nerves, protein crystalloids and starch granules. The numerous figures and sketches are well presented, and