The Mastigophora 151 



some species. The usual single chromatophore is cup-shaped (Fig. 4. 26, 

 B). However, lobed, "H-shaped," and other variations are known (Fig. 4. 

 26, D-J). The nucleus lies in the inner zone of cytoplasm. One or more 

 pyrenoids, typically spherical or ellipsoidal, but sometimes U-shaped (Fig. 

 4. 26, K, L), are characteristic of green species. A single pyrenoid usually 



Fig. 4. 26. AC. Flagellar insertions, schematic: A, Chlamydomonas na- 

 suta (after Kater); B. C. longirubra (after Pascher); C. C. ignova (after 

 KorshikofF). D-J. \'arious types of chromatophores; pyrenoids indicated as 

 clear areas; schematic: D. Chlamydomonas obversa (after Pascher); E. Chlo- 

 rogonium elongatiim (after Dangeard); F, G. Chlamydomonas ovata (after 

 Dangeard); H. C. basistellata (after Pascher); I. C. korschikoffia (after 

 Pascher); J. Gigaiitochloris permaxima (after Pascher). K, L. Unusual U- 

 shaped pyrenoid; optical cross-section and lateral view of flagellate; starch 

 granules surround the pyrenoid; diagrammatic (after Vlk). 



lies in the posterior portion of the cup-shaped chromatophore; if several 

 pyrenoids are present, distribution is variable. A stigma, when present, 

 is a rounded or discoid structure, usually anterior in position but some- 

 times near the equator. Starch, stored both in the cytoplasm and around 

 the pyrenoid of chlorophyll-bearing species, occurs also in colorless types. 

 Lipids, although usually not abundant, are stored by many phytoinonads. 

 A reddish pigment (red haematochrome) also may be accumulated in the 



