CYTOPLASMIC INCLUSIONS 113 



in life, become grey brown, or black in osmic techniques, but usually 

 bleach faster than the Golgi bodies, reduce pyrogallol, take basic stains 

 after fixation in lipoid preservatives, stain weakly or not at ail after fixa- 

 tives containing acetic acid, and are stained vitally with janus green B. 

 This last method is often considered to be the final criterion, but un- 

 fortunately in many cases the mitochondria of Protozoa stain only a pale 

 green (Subramaniam and Ganapati, 1938, and others), not the dark 

 green described in metazoan cells. In addition, the stain is not always 

 specific, since Lynch (1930) found that any concentration from 1:2000 

 to 1:500,000 tints the entire organism [Lechriopyla), although the 

 mitochondria can be distinguished by their darker color. Hayes (1938) 

 found that none of the granules in Dileptus stained electively with Janus 

 green B. An additional source of difficulty is the fact that in flagellates, 

 the parabasal bodies are often stained as darkly as the mitochondria. 

 Although the parabasal bodies and mitochondria show additional simi- 

 larities in staining reactions and composition, Volkonsky (1933) points 

 out that the former are derivatives of the neuromotor system and cannot 

 be considered as homologous with the mitochondria. 



Mitochondria present a wide variety of shapes, but most commonly 

 they are spherules (Fig. 17), chains of spherules (Fig. 26), short rods 

 (Figs. 22, 23), or dumb-bells. The filamentous structures found so often 

 in metazoan cells are found rarely in the Protozoa, but a good example 

 has been described in the phytoflagellate Polykrikos by Chatton and 

 Grasse (1929). Lynch (1930), in his studies on the ciliate Lechriopyla, 

 found a compound structure (Figs. 15. 16), composed of several discs. 

 Each disc is composed of chromophobic material, with a rim of chromo- 

 philic material which stains with Janus green and the other mitochondrial 

 dyes. In cases of secretion (Fig. 17), the secretion granules often appear 

 as a chromophobic center in the mitochondria (MacLennan, 1936), but 

 the mitochondrial material itself usually appears to be homogeneous 

 either in the living unstained ciliate or after any of the mitochondrial 

 stains. It is probable that the chromophobic center of the discs of 

 Lechriopyla represents material secreted by the rim, which is the mito- 

 chondrial part of the complex discs. In some cases, however, mitochondria 

 may have a true duplex structure, since Mast and Doyle (1935b) showed 

 that the outer surface of the mitochondria of Amoeba stain more deeply 

 than the center. This diff^erentiation may be explained either as a definite 



