ZOOFLAGELLATES 141 



pinocytosis in vertebrate capillary epithelia and other cells that 

 take up complex molecules makes the observation of the same 

 phenomenon in blood parasites less than surprising. The 

 existence of a highly specialized locus for this process is, however, 

 unexpected. Although various intracellular fibers in trypanosomes 

 have been reported by light microscopists, it is not certain 

 whether any of these may correspond with the fibrous tube. If a 

 similar structure exists in all other trypanosomes, or at all life- 

 cycle stages, one would expect other investigators to have seen 

 it in electron micrographs. Clark (personal communication) 

 reports that he has encountered it very rarely in a series of species 

 studied by him. 



Pyne (1959, 1960b) has published two reports from a continuing 

 investigation of Cryptobia helicis, a bodonid symbiotic in a garden 

 snail, while the very common, free-living Bodo saltans is under 

 study by Pitelka (1961b and unpublished). The two genera have 

 many morphological features in common. Both have long trailing 

 and shorter anterior flagella arising from a more or less pro- 

 nounced anterolateral depression, near the base of which is an 

 ovoid kinetoplast. 



In both species, the flagellar membrane encloses, in addition to 

 the 11 axial fibrils, a paraflagellar rod of dense material (Fig. 51, 

 PL XIII) which in appropriate cross-sections is seen to be com- 

 posed of six to eight flat bands about 7 m/z thick. This material 

 originates immediately distal to the kinetosome and extends for 

 an indeterminate distance along the flagellum — terminal sections 

 lacking the rod are frequently encountered. The trailing flagellum 

 of Cryptobia adheres in life to the whole length of the cell body. 

 No physical connection is seen in electron micrographs, but the 

 flagellum occupies a groove in the cell surface. 



In both Cryptobia and Bodo, the kinetosomes project for a short 

 distance into the circumflagellar depression. Basally, they stand 

 in intimate contact with the limiting membrane of the kinetoplast. 

 This body resembles the kinetoplast of the trypanosomes, but 

 shows no pronounced orientation in the filamentous network 

 occupying its center (Fig. 50, PI. XIII). Peripherally, membranous 

 profiles resembling mitochondrial cristae are present, and two 

 unit membranes bound the organelle. In light-microscope 

 preparations of Bodo saltans, a "cordon siderophile" (Hollande, 



