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a science that deals with unicellular eu-caryotic organisms of the phylum Protozoa. The scope and content of protistology are interpreted in different ways.

Some scientists (the Soviet V. A. Dogel’, the German J. E. Reichenow, the French P. Grassé) limit protistology to the study of unicellular animals with a heterotrophic mode of feeding and lower unicellular and colonial green organisms with an autotrophic mode of feeding (Chlamydomonas, Volvocophy-ceae, Dinoflagellata, and some others). They classify autotrophic unicellular organisms equipped with flagella in the class Flagellatae and divide the class into several orders (Phytomo-nadina, Euglenina, Dinoflagellata).

Other scientists (the Russian botanist Kh. Gobi, the Soviets E. M. Kheisin and Sh. D. Moshkovskii) believe the Protozoa should embrace only unicellular heterotrophic organisms and that autotrophic organisms with chlorophyll should be treated as algae. If this interpretation is accepted, then protistology is a synonym of protozoology, which is a zoological science.

However, there exist unicellular organisms (for example, many Euglenina) with a mixotrophic, that is, autotrophic and heterotrophic, type of feeding. Moreover, some taxonomically close forms often have chlorophyll and are typical autotrophs (for example, species of the genus Chlamydomonas), whereas some similar forms (Polytoma) are heterotrophs. All this implies that eucaryotic plants and animals have a common origin.

Protistology is closely allied with many theoretical and applied sciences, including cytology (the objects of study of protistology—protozoans—are organisms at the cellular level of organization), various branches of medicine and veterinary science (many parasitic protozoans are the causative agents of serious diseases of man and animals, including farm animals), parasitology, hydrobiology, ecology, and paleontology.

In addition to microscopy, protistology uses cytological and cytochemical methods, including photometry and autoradiography. Study of the ultrastructure of protozoans by electron microscopy and the raising of protozoans in culture have become very important. Serologic and immunologic methods are used to investigate parasitic protozoans.

The study of protozoans, which began in the late 17th century, was made possible by the invention of the microscope by the Dutch naturalist A. van Leeuwenhoek. Using the primitive microscope that he constructed, he discovered the world of microscopic beings, which comprised the protozoans. The work Animalcula infusoria (1786) by the Danish zoologist O. F. Müller, who described more than 370 species of microscopic organisms (mostly protozoans), stimulated further study of these organisms.

However, in the 18th and early 19th centuries, scientists had conflicting views on the nature of protozoans. For example, the German naturalist C. G. Ehrenberg in his monograph Infuserions as Complete Organisms (1838) described protozoans as complexly organized beings having all the organ systems characteristic of other animals and differing from other animals only in their microscopic size. The concept of protozoans as unicellular organisms was first formulated in 1845 by the German scientist K. von Siebold. This correct view of the nature of protozoans was later elaborated further by the German protis-tologist O. Bütschli. The study of sporozoans—the causative agents of several diseases—attracted considerable attention at the end of the 19th and the beginning of the 20th century. F. Schaudin (Germany) established the principal stages in the life cycle of coccidians, and V. Ia. Danilevskii (Russia), J. Ross (Great Britain), and G. Grassi (Italy) determined the life cycles of haemosporidians, including the causative agent of malaria.

The number of studies on protozoans increased rapidly in the 20th century owing to the organisms’ theoretical and practical significance. Major contributions have been made by G. Calkins, L. Woodruff, H. Jennings, T. Sonneborn, C. Kofoid, and H. Kirby in the United States; R. von Hertwig, M. Hartmann, F. Doflein, and J. E. Reichenow in Germany; E. Maupas, E. Chatton, and E. Fauré-Fremiet in France; C. Dobell and C. Wenyon in Great Britain; and S. I. Metal’ni-kov, V. T. Sheviakov, and others in the USSR. Research is being conducted on physiology, forms of reproduction, alternation of generations, the role of the sexual process, and variability and heredity at the cellular level of organization. The study of protozoans is becoming increasingly involved with problems of cytology and general biology. Medical protozoology and veterinary protozoology arose in the 20th century as independent disciplines with important practical objectives.

Russian and Soviet scientists have made substantial contributions to the development of protistology. In the first half of the 20th century, G. I. Roskin, N. K. Kol’tsov, and especially V. A. Dogel’ (who founded a major scientific school) dealt with general problems of protistology. E. I. Martsinovskii, V. A. Ro-manovskii, Sh. D. Moshkovskii, N. I. Latyshev, G. V. Epshtein, A. A. Filipchenko, V. G. Gnezdilov, and Sh. G. Matevosian have done important work in medical protozoology. Considerable research in veterinary protozoology has been done by V. L. Iakimov and A. A. Markov.

Protistological or protozoological societies exist in a number of countries. The All-Union Society of Protozoologists was founded in the USSR in 1968. Specialized journals are published in the German Democratic Republic, Poland, the United States, and France. The German Archiv für Protistenkunde (Jena, since 1902) is the oldest of such journals. International congresses have been held regularly every four years since 1961; the third was held in the USSR (Leningrad) in 1969 and the fourth was convened in France (Clermont-Ferrand) in 1973.


Epshtein, G. V. Patogennye prosteishie, spirokhety i gribki. Moscow-Leningrad, 1931.
Iakimov, V. L. Bolezni domashnikh zhivotnykh, vyzyvaemye prosteishimi (Protozoa). Moscow-Leningrad, 1931.
Brodskii, A. L. Istoriia protozoologii. Tashkent-Samarkand, 1937.
Dogel’, V. A. Obshchaia protistologiia. Moscow, 1951.
Wenyon, C. M. Protozoology, vols. 1–2. London, 1926.
Doflein, F., and J. E. Reichenow. Lehrbuch der Protozoenkunde, 6th ed., vols. 1–2. Jena, 1949–53.
Traité de zoologie, vol. 1, fascs. 1–2. Edited by P. Grassé. Paris, 1952–53.
Research in Protozoology, vols. 1–4. Edited by Tze-Tuan Chen. Oxford, 1967–72.