PHYTOFLAGELLATES 129 



concentric rings of material resembling the nucleolar substance, 

 lying in a concavity of the endosome. 



Peranema trichophorum is a colorless biflagellate euglenoid that 

 ingests particulate food through a permanent cytostome located 

 next to the external opening of the reservoir canal. Since this is 

 the first instance we have encountered, and one of the few known 

 among the flagellates, of a specialized mouth structure, it is of 

 particular interest. Its ultrastructure has been examined by Roth 

 (1959). The living cell has a slender, rounded anterior end during 

 normal swimming. In this position the cytostomal opening is 

 small and obscure, but a pair of conspicuous, tapering rods, the 

 pharyngeal rodorgan, lies next to the reservoir. The cell may feed 

 on Huglena or other organisms as large as itself, either by ingesting 

 them whole or by attacking them in small bites. During the 

 latter process the pharyngeal rods are in vigorous movement, 

 acting together apparently as a puncturing tool, probe, and lever 

 (Chen, 1950a). The anterior end of the cell may be widely 

 extended, permitting large ingesta to enter a food cup which 

 always is separated from the smaller reservoir by the rodorgan 

 (Pitelka, 1945). A system of what appear in stained specimens in 

 the light microscope to be fibers articulates with the anterior 

 ends of the rods ; these surround the cytostome incompletely at 

 rest and unfold during ingestion. 



Roth's electron micrographs show that each pharyngeal rod 

 (Fig. 48, PI. XIII) is composed of a bundle of approximately 100 

 parallel, hexagonally packed tubular fibers, each about 26 m/x in 

 diameter. Surrounding this bundle for most of its length is a 

 dense, homogeneous zone and a heavy limiting membrane. The 

 two rods are joined by a bridge at their anterior ends. The 

 articulated cytostomal fibers actually are several sheet-like pro- 

 cesses with a beaded or fibrillar structure. These insert in grooves 

 on the pharyngeal rods at two different levels. Roth speculates 

 that the sheets are contractile and thus are responsible for the 

 movements of the rodorgan, which itself always moves as a rigid 

 unit. This seems likely, and one would like to have more informa- 

 tion on the detailed configuration of the sheets. To account for 

 the energetic movements of the rodorgan, the sheets would have 

 to attach somewhere to another structure with some tensile 

 strength, and this probably could only be the pellicle. That such 



