40 General Morphology of the Protozoa 



Mitochondria 



Mitochondria (or chondriosomes), which seem to be generally 

 present in Protozoa, were observed as early as 1910 in Chilomonas, Cryp- 

 tomonas, and Noctihica (54). Subsequently, mitochondria have been 

 described in many species (76, 77, 158). Mitochondria are to be expected 

 in Protozoa during the active phase of the life-cycle, but may be absent in 

 the cyst, as reported for Ichthyophthirhis multifiUis, in which the mito- 

 chondria disappear rapidly after encystment (156, 159). Reportedly mito- 

 chondria-free sporozoites of Monocystis (94) may be an analogous case. 

 In addition, mitochrondria have not been found in active stages of a 

 marine amoeba, FlabeUula mira (89). 



Mitochondria may occur as granules, short rods, filaments, or fila- 

 mentous networks. The form is more or less characteristic of a species, 

 although some variation may be expected. Filamentous mitochondria 

 (Fig. 1. 19, A), apparently less common than other types, have been 

 described in Chlorogonium, Chlamydomonas, and Polytoma. Such fila- 

 ments are often anastomosed in a superficial network. Mitochondrial nets 

 also have been observed in green and colorless strains of Euglena gracilis 

 (95). Similar networks, which occasionally break up into short rods, occur 

 in Glenodiyiium sociaJe and other dinoflagellates (7). These inclusions 

 are usually stainable vitally with Janus green B, although the reaction 

 may be less intense than that of metazoan mitochondria. Good results 

 have also been reported with Janus red (91). Special fixatives, such as 

 the chromate-osmic mixtures, are advisable for good permanent prepara- 

 tions. 



The cytoplasmic distribution of mitochondria varies with the species. 

 Random cytoplasmic distribution (Fig. 1. 19, B) is common, but aggrega- 

 tion around food vacuoles is sometimes noted (166). The mitochondria 

 of Chilomonas (Fig. 1. 19, D) and Cryptomonas, as well as those of Phy- 

 tomonadida and Euglenida, are believed by Hollande (88) to be entirely 

 peripheral. Certain endoplasmic inclusions of these flagellates, previously 

 interpreted as mitochondria after demonstration with mitochondrial tech- 

 niques (76, 77), are said to be cytoplasmic vacuoles. Peripheral mitochon- 

 dria of ciliates may be oriented in rows, as in Nyctotherus cordiformis 

 (93). Association of peripheral mitochondria with the basal granules has 

 been described in Colpidiiim colpoda and other ciliates (26), but this is 

 not the case in Tillina canalifera (213). Mitochondria of Bursaria truri- 

 catella are mostly peripheral during conjugation but are scattered through 

 the cytoplasm in other phases of the life-cycle (181). 



Various functions have been assigned to the mitochondria. Morpho- 

 genetic interpretations include a mitochondrial origin of pyrenoids (20) 

 and the derivation of Golgi material, parabasal bodies, blepharoplasts, 

 and the stigma from mitochondria (1). Supposed physiological activities 



