Plasm: the colloid or jelly-like matter of which organisms are composed; hence:— Caryoplasm: the matter of the nucleus (_caryon_). Cytoplasm: the matter of the body of the cell. Deutoplasm: secondary or differentiated plasm. Metaplasm: secondary or differentiated plasm. Protoplasm: primitive or undifferentiated plasm. Plasson: the simplest form of plasm. Plastidules: small particles of plasm. Polyspermism: the penetration of more than one sperm-cell into the ovum. Pro- or Prot: (in compounds) the earlier form (opposed to Meta); hence:— Prochorion: the first form of the chorion. Progaster: the first or primitive stomach. Pronephridia: the earlier form of the kidneys. Prorenal: the earlier form of the kidneys. Prostoma: the first or primitive mouth. Protists: the earliest or unicellular organisms. Provertebræ: the earliest phase of the vertebræ. Protophyta: the primitive or unicellular plants. Protoplasm: undifferentiated plasm. Protozoa: the primitive or unicellular animals. Renal: pertaining to the kidneys (_renes_). Scatulation: packing or boxing-up (_scatula_ = a box). Sclerotomes: segments into which the primitive skeleton falls. Soma: the body; hence:— Cytosoma: the body of the cell (_cytos_). Episoma: the upper or back-half of the embryonic body. Somites: segments of the embryonic body. Hyposoma: the under or belly-half of the embryonic body. Teleology: the belief in design and purpose (_telos_) in nature. Telolecithal: see Lecith-. Umbilical: pertaining to the navel (_umbilicus_). Vitelline: pertaining to the yelk (_vitellus_). PREFACE [BY JOSEPH MCCABE] The work which we now place within the reach of every reader of the English tongue is one of the finest productions of its distinguished author. The first edition appeared in 1874. At that time the conviction of man’s natural evolution was even less advanced in Germany than in England, and the work raised a storm of controversy. Theologians—forgetting the commonest facts of our individual development—spoke with the most profound disdain of the theory that a Luther or a Goethe could be the outcome of development from a tiny speck of protoplasm. The work, one of the most distinguished of them said, was “a fleck of shame on the escutcheon of Germany.” To-day its conclusion is accepted by influential clerics, such as the Dean of Westminster, and by almost every biologist and anthropologist of distinction in Europe. Evolution is not a laboriously reached conclusion, but a guiding truth, in biological literature to-day.