PROTOZOA AS CELLS 17 



Biochemical studies by Kuff and Dalton (1959) on Golgi 

 membranes isolated from rat epididymis indicated a concentration 

 there of lipid phosphorus and acid phosphatase, but no unique 

 biochemical properties were found. In general, the assumption 

 that the Golgi apparatus functions in secretory activities is borne 

 out by its appearance in many vertebrate cells where, for example, 

 granules of zymogen (Palade, 1959) or of milk protein (Wellings 

 and DeOme, 1961) accumulate within Golgi membranes to form 

 aggregates that may then move elsewhere in the cell, still enclosed 

 in Golgi-derived vacuoles. In most protozoa — and most other 

 cells where secretion products are less conspicuous or less 

 intensively produced — good clues to the function of the Golgi 

 complex are lacking. 



Mitochondria 



Mitochondria are another kind of membranous organelle that 

 has a highly characteristic and remarkably uniform structure in 

 all eucells. Whatever their size or shape, mitochondria are limited 

 by two unit membranes, separated by a gap of about 10 m/x. 

 Internally there are additional membranes arranged usually in the 

 shape either of flat shelves called cristae or of convoluted micro- 

 tubules. These appear to be continuous with the inner one of the 

 two limiting membranes, as though they were formed as internal 

 extensions of it. Variations in the abundance and in the orienta- 

 tion of the cristae or microtubules are common; rarely, very 

 orderly patterns are found. The matrix surrounding the internal 

 membranes varies in density and has little visible structure, but 

 inclusions often appear in the form of small dense bodies or 

 bundles of fine filaments. 



Mitochondria in most cells of metazoa and of land plants have 

 internal cristae. Microtubular mitochondria (Fig. 2, PI. I) are 

 characteristic of the majority of protozoan types studied to date, 

 but also occur in an odd assortment of other cells (Sedar and 

 Rudzinska, 1956; Rouiller, 1960; NovikofT, 1961). Among the 

 flagellates, both types, and perhaps some intermediates, are seen. 

 Chrysomonad flagellate mitochondria are microtubular; most 

 green algae and euglenoids (Fig. 4, PL I) examined have cristae. 

 In a relatively simple zooflagellate, Bodo, a mitochondrion of 



