142 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



1952c) arises from the kinetoplast, makes a complete longitudinal 

 loop around the cell, and rejoins the kinetoplast. That this cord 

 in all probability is a mitochondrion is indicated by its ultra- 

 structure as shown in Figs. 1 and 5, PL I. The similarity to the 

 situation demonstrated by Steinert in Trypanosoma mega is obvious, 

 but the length of the single, continuous mitochondrion in Bodo 

 seems to be unique. Pyne has not commented on mitochondria 

 in Cryptobia. 



Both species possess well-developed Golgi zones. In Bodo this 

 occupies a constant position anterior and lateral to the kinetoplast 

 and is often associated with large vacuoles. No fibrous connection 

 to the kinetosome region is observed. Granular cytoplasmic 

 membranes are seen in both species; in Bodo the cytoplasm is 

 particularly rich in Palade particles. Food vacuoles containing 

 bacteria are abundant; the contractile vacuole has not been 

 distinguished from other, unidentified empty vacuoles. 



The pellicle of Cryptobia is very similar to that of the trypano- 

 somes ; an outer unit membrane is underlain by a layer of parallel 

 tubular fibrils, about 25 m/x in diameter. Fibrils in the wall of 

 the flagellar depression appear thicker than those in the pellicle. 

 Within the cytoplasm, two groups of tubular, 20 m/x fibrils are 

 reported, leading away from the kinetosomes. 



In Bodo, most of the body is limited by a unit membrane with 

 no accompanying fibrils. But several sets of tubular fibrils, about 

 20 m/x in diameter, arise from the bases of the kinetosomes. Some 

 of these directly connect the two kinetosomes ; others run up the 

 walls of the flagellar depression, immediately beneath the cell 

 membrane, then curve around the asymmetric anterior tip of the 

 cell and converge in an open apical cup. The latter corresponds 

 to the rostral vacuole seen in the light microscope (Hollande, 

 1952c). From one side of this apical cup a group of fibrils 

 descends into the cytoplasm, closely resembling the "cytostomal" 

 tube of Trypanosoma mega described by Steinert and NovikofT 

 (1960). In Bodo, however, the tube remains open, and lined by an 

 invagination of the cell membrane, deep into the cell (Fig. 52, 

 PL XIV). The cylinder of fibers terminates at the surface of the 

 kinetoplast, adjacent to the kinetosomes of the flagella. In fact, 

 the whole fibrous tube resembles a modified intracytoplasmic 

 flagellum, lacking central fibrils and being instead lined by a 



