small embryonal chamber, represent different stages in the same life history. He elucidated the life cycle of Calcituba, and discovered in it a simple and probably very primitive mode of cell division. The division of the Amœba with two nuclei (Amœba binucleata) was described, and from Schaudinn dates the concept that the original cell possessed two nuclei. Then he described the copulation of the Heliozoan Actinophrys, which was the first account of reduction of the chromatin and caryogamy of any protozoan, compared the processes here with the similar ones in the many-celled animals, and showed that the central granule acted as a centrosome. Conjugation of the spores was also discovered in Hyalopus, a foraminiferan; and his discovery of the paranucleus of Paramœba has come to greatly modify the older ideas on the genesis of the cell nucleus. These discoveries rapidly succeeded each other, marked a great advance over all preceding studies on the reproduction phenomena of the protozoa, and stimulated others to the same field of study.
Next he turned himself to the analysis of the life cycles of parasitic protozoa, a study of particular difficulty because all such parasites live in successive different hosts. Most men have failed in these studies because they lacked the fertility and resource of Schaudinn in devising experiments. Monumental was his study on the complete life cycle of a coccidian (a sporozoan), a parasite of a centipede (Lithobius), made in conjunction with Siedlecki. This gave for the first time the complete history of any sporozoan, and was soon followed by an equally conclusive and thorough research, extending through five years, of the life cycle of Trichosphærium. These are classics in the study of the protozoa, and they showed the method by which results are to be reached in the search of the parasites of human disorders. In each of these life cycles there follow upon each other a long line of generations, with great dissimilarity of the successive generations; Schaudinn drove home the conclusion that the unit of study should be the whole life cycle, and his results rendered it probable that many forms of protozoa that had hitherto been regarded as different species might be merely stages of one and the same life cycle. This was one of his major contributions that guided him in his later work and has caused an entire change in progressive medicine.
Schaudinn then left Berlin to become director of the laboratory at Rovigno, on the Adriatic Sea, whither he was called primarily to contribute to the study of the malaria organisms. There he first worked out the life history of Cyclospora, the agent of enteritis of the mole, carrying out his method to approach human disorders from a preliminary broad comparative basis. Then he made a valuable contribution to the history of Plasmodium vivax, the cause of tertian fever in man; and was the first to see the sporozoites entering living human