1028 PARASITES OF PROTOZOA 



symbionts with as much justification as may the microorganisms in the 

 bacteriocytes and mycetocytes of certain insects. Pierantoni (1936) pro- 

 posed a hypothesis concerning the function of bacteria in flagellates of 

 termites. According to this hypothesis, with which Grasse (1938) ex- 

 pressed agreement, the bacteria function in the xylophagous nutrition 

 of the flagellates. The flagellates, which are unique among Protozoa 

 in their xylophagous habits, are, like so many wood-ingesting animals, 

 incapable of digesting cellulose, but depend upon symbiotic bacteria. 

 The bacteria are sometimes localized in "symbiotic organelles," some- 

 times diffusely distributed in the cytoplasm. The hypothesis rests on 

 grounds similar to that of the supposed role of the intracellular symbionts 

 in insects — the constant association and frequent localization suggest 

 the likelihood of a fundamental significance in the relationship. The 

 weakness of both hypotheses is patent; there is no physiological evi- 

 dence in their support. Furthermore, the existence of "organelles" of 

 the type mentioned is exceptional in xylophagous flagellates. 



It is probable that the so-called chromidial zone of Joen'm annectens 

 is a bacterial aggregate. It occurs constantly in that hypermastigote, 

 and has been shown or described by all students of the flagellate (Grassi 

 and Foa, 1904, 1911; Franca, 1918; Duboscq and Grasse, 1928, 1933, 

 1934; Cleveland et al., 1934; Pierantoni, 1936). According to Duboscq 

 and Grasse, the bodies in this group are rods. The group surrounds the 

 axostyle posterior to the nucleus, often forming a broad ring. Duboscq 

 and Grasse (1934) figured an instance in which they form a spherical 

 group, not encircling the axostyle, in a nondividing flagellate; and ap- 

 parently in division stages they disperse. In the figures presented by 

 these authors there are forms of the small rods that might be interpreted 

 as division stages. 



Grassi and Foa (1911) concluded that the area they earlier called 

 the chromidial zone acts as a phagocytic organ, since in experimental 

 feeding they found granules of carmine included in it. Duboscq and 

 Grasse regarded the rods as mitochondria, but their reaction to fixatives 

 and stains rather suggests bacteria. They are resistant to fixatives after 

 which true mitochondria are not demonstrable. Pierantoni considered 

 them to be bacteria, and showed difl^erential staining of them and mito- 

 chondria in Altmann-KuU. 



The writer has observed a comparable aggregate of granules or rods 



