PROTOZOA AS CELLS 



13 



and shapes. Certain consistent configurations of membranes 

 constitute identifiable organelles that will be described presently. 

 It has become common practice to refer to any other small 

 membranous elements as "endoplasmic reticulum" (Text-fig. 1), 



Text-figure 1. Diagrammatic reconstruction of part of idealized 

 cell containing organelles characteristic of many cell types. From 

 Wohlfarth-Bottermann, 1960a: Icm, Invagination of cell membrane, 

 a. surface view, b. section; Er, Endoplasmic reticulum; Mm, 

 Mitochondrion (microtubule type); Nm, Nuclear membrane; N, 

 Nucleolus; C, Centriole; Gz, Golgi zone; Cs, Cell surface; Cm, 

 Cell membrane; Ld, Lipid droplet; Pp, Palade particles, E, 

 Ergastoplasm ; Np, Nuclear pore, a. section, b. surface view; 

 Mc, Mitochondrion (crista type). 



whether or not they are exclusively endoplasmic or demonstrably 

 reticular. This term was introduced by Porter and Kallman 

 (1952) to describe a system of tubes and sacs ramifying through 

 the cytoplasm of thin whole mounts of tissue culture cells. 

 Because of this observation, and because various membranous 

 structures are frequently seen in sections to be interconnected 

 (very extensively so in some higher plant cells), it has been 

 suggested that the entire protoplasm is segrated into a continuous 



