126 CYTOPLASMIC INCLUSIONS 



two types of reserve granules, the existence of a secretory function is 

 possible, and it is not necessary to invoke respiration in order to find 

 a function for these mitochondria. The respiratory function must be 

 regarded as unproved, either from the standpoint of the proof of the 

 presence of materials which could act as an oxidation-reduction system, 

 or from the standpoint of the direct measurement of localized oxidation- 

 reduction potentials. At best mitochondria as morphological entities 

 cannot be necessary for respiration, since many species lack them at one 

 time or another in the life cycle, and since in other cases they can be 

 eliminated experimentally without fatal results (Kirby, 1936). 



All the various types of evidence — staining reactions, composition, 

 function, and tracing through the life history — show that mitochondria 

 in the Protozoa do not form a homogeneous group, but are actually a 

 heterogeneous assortment which are associated merely by their ability 

 to segregate Janus green B or by even less specific staining reactions. No 

 one type is found in all Protozoa, and in all cases which have been 

 carefully studied mitochondria are not self-perpetuating but arise de 

 novo at some time during the life cycle. 



The Vacuome Hypothesis 



According to the vacuome hypothesis as applied in the Protozoa, there 

 are only two fundamental cytoplasmic components in the Protozoa — the 

 chondriome and the vacuome, since the Golgi bodies and vacuome are 

 merely different aspects of the same thing. The term vacuome was 

 substituted for the earlier term segregation granule as an indication of the 

 supposed homology between the neutral red bodies in animal cells and 

 the vacuoles of plant cells. Volkonsky (1929 on), Kedrowsky (1931- 

 33), Hall and his associates (1929 on), Lynch (1930), and others have 

 upheld the general conclusion that the granules stainable with neutral 

 red are identical with the Golgi bodies; but Kirby (1931), MacLennan 

 (1933, 1940), Bush (1934), Kofoid and Bush (1936), Daniels 

 (1938), and others have demonstrated many cases of neutral red 

 granules which are not osmiophilic (for a more detailed discussion of 

 this point, see p. 140). It should be pointed out that the acceptance 

 of the vacuome hypothesis is by no means universal in the Metazoa or 

 Metaphyta, according to Weier (1933) and Kirkman and Severinghaus 

 (1938). 



