PHYTOFLAGELLATES 119 



little group of golgi vesicles, one fat body, one flagellum, and a 

 very small amount of residual cytoplasm, it seems doubtful 

 whether any further reduction would be possible without 

 involving the fundamental structure of the organelles themselves." 

 The organelles have to be small to fit into a 1 n body, but they 

 appear no simpler in structure than their counterparts in other 

 cells. The flagellum and kinetosome are, except for the shortness 

 of the flagellum, of conventional dimensions. The sparseness of 

 mitochondrial membranes and the apparent lack of flat cisternae 

 in the presumed Golgi area cannot be taken as evidence of 

 structural simplicity, since these features are known to vary with 

 the metabolic states of cells. Whether M. pusilla is primitively or 

 secondarily restricted to one of everything, it might provide an 

 extraordinarily useful tool for the biochemist. It should be possible 

 to obtain serial sections through an entire cell, and from them to 

 calculate the actual total membrane area of the chloroplast and 

 mitochondrion, for example. From estimated molecular dimen- 

 sions, one could arrive at a figure approximating the number of 

 macromolecules required to sustain the measurable metabolic 

 activities of the cell. 



M. squamata (Manton and Parke, 1960) is similar to M. pusilla 

 in most respects, but in addition to its larger size (3-5 fi diameter) 

 shows some interesting structural peculiarities. Like M. pusilla, 

 it has a single large plastid with peripheral discs and a dense, 

 eccentric pyrenoid surrounded by starch shells, a single mito- 

 chondrion, and a Golgi zone near the kinetosome of the single, 

 posteriorly-directed flagellum. The mitochondrial membranes in 

 the published micrographs appear to be microtubular, and the 

 Golgi element is much more distinctly developed than it seemed 

 in M. pusilla. The chloroplast contains a region of close-packed 

 vesicular chambers identifiable as a stigma. Discontinuities in 

 the chloroplast discs appear in surface view as rather uniformly 

 distributed holes penetrating several discs. A single fibrous 

 rhizoplast originates at the base of the kinetosome, passes through 

 the cytoplasm parallel to the kinetosome and terminates at the 

 adjacent nuclear membrane. 



Of considerable interest is a coating of regularly overlapping, 

 submicroscopic scales all over the surface of the body and of the 

 flagellum. These are slightly mineralized, flat discs with a spider- 



