THE GOLGI APPARATUS OF PROTOZOA

(i) The Golgi apparatus is considered to be a definite cellular inclusion in the Protozoa, although there is still considerable disagreement regarding identification, morphology, distribution, and function in the different classes. (2) The osmic techniques of Weigl (Mann‐Kopsch) and Kolatchew, followed by bleaching in hydrogen peroxide or turpentine, are specific for the Golgi material in most organisms. The silver methods of Cajal and Da Fano are seldom successful in the Protozoa. The application of the ultra‐centrifuge has proved that the neutral‐red bodies, i.e. the ‘vacuome’, are not identical with the Golgi bodies. (3) In the Mastigophora the parabasal bodies of many forms are considered to represent the Golgi apparatus, though the homology may not be said yet to be fully proved. In other flagellates the cortex of the contractile vacuole is impregnated by the osmic Golgi techniques and its behaviour during division in many organisms is similar to that of the metazoan apparatus. These criteria seem sufficient to identify it as Golgi material. (4) In the Sporozoa there is general agreement that the Golgi apparatus is represented by scattered globules or dictyosomes, often possessing osmiophile and osmiophobe regions. In some cells it shows the juxta‐nuclear position so characteristic of the Golgi apparatus of many metazoan cells. The homology is also supported by the fact that in the centrifuged sporozoan the osmiophile material occupies the same position relative to the other inclusions as does the Golgi material in higher animal cells. (5) There is still much confusion as to the exact nature of the Golgi apparatus in the Khizopoda, and there is little agreement as to its identity in any of the types studied. Some workers have described the Golgi apparatus as being represented by scattered osmio‐philic globules or granules. Others have failed to identify any Golgi material in members of this class. (6) In the Ciliata most workers agree that the osmiophile cortex to the contractile vacuole found in many forms represents the Golgi apparatus. In some instances scattered Golgi bodies are distributed throughout the cytoplasm. These are often present in combination with the Golgi cortex. There is no convincing evidence that any Golgi material is present in sea‐water ciliates, the fresh‐water form Stytonychia, or the parasitic Nyctotherus. (7) Nassonow's view that the osmiophile material together ivith the contractile vacuole represented the Golgi apparatus is not supported by modern workers. The osmiophile material alone is believed to represent this inclusion. There is much evidence to suggest that there is a single type of granular Golgi body, from which both the osmiophile cortex type and the dictyosome type are formed. It is likely that the Golgi apparatus arose in connexion with the base of the flagellum, later becoming associated with the vacuolar system in many forms. (8) In view of the great diversity in form of the protozoan Golgi apparatus any single hypothesis regarding function is inadequate to explain all the facts. There is much evidence, however, to indicate that it is concerned with the mechanism of excretion or secretion, and possibly also with the osmoregulation of the organism. In the Sporozoa it may take part in fat metabolism.