The Mastigophora 133 



spheroid; that of Phaeoplaca Chodat (90), discoid; and the matrix of 

 Phaeosphaera West and West (202) is cylindrical and sometimes 

 branched. 



Family 2. Celloniellidae. Fission does not occur throughout the pal- 

 mella. Instead, growth of the palmella depends upon fission in particular 

 groups of cells which produce new points of growth. In the sessile 

 Celloniella Pascher (Fig. 4. 12, A-E), the form of the palmella varies 

 with rate of flow of the water in which the mass is suspended (209). 



Family 3. Hydruridae. Hy drums Agardh (152, 202) resembles Celloni- 

 ella, but the palmella is profusely branched and sometimes reaches a 

 length of 25-30 cm. Furthermore, fission apparently is limited to the 

 apical flagellates in each branch. 



Family 4. NagelieUidae. Species of Nageliella Correns (202, 248), 

 usually epiphytic on algae, develop a somewhat discoid palmella from 

 the free surface of which extends a bundle of gelatinous filaments. In 

 N. natans (Fig. 4. 12, F) each filament contains an axial fibril which arises 

 from the apical end of each flagellate (248). 



Order 2. Heterochlorida 



These flagellates have a flexible periplast, typically two unequal 

 flagella, and one or more pale yellow-green or pale yellow chromato- 

 phores. The occurrence of pyrenoids is doubtful. Leucosin and lipids 

 are stored. 



Endogenous encystment (Fig. 4. 13, A-D) is known in Chloromeson 

 and Myxochloris (216). Unlike that in Chrysomonadida, the cyst wall 

 is composed of two unequal valves and lacks a pore. In addition to the 

 encystment of uninucleate stages, an entire plasmodium of Myxochloris 

 sphagnicola may become enclosed in a membrane apparently containing 

 pectins (213). 



On the basis of life-histories, the Heterochlorida may be divided into 

 three suborders: Euheterochlorina, with a dominant flagellate stage; 

 Rhizochloridina, with a dominant non-flagellated or plasmodial stage; 

 Heterocapsina, with a dominant palmella. 



Suborder 1. Euheterochlorina. Representative types (Fig. 4. 13) in- 

 clude Chloromeson Pascher (31, 212, 216), Nephrochloris Geitler and 

 Gemisi (31), and Olithodiscus Carter (31). 



Suborder 2. Rhizochloridina. Myxochloris Pascher (Fig. 4. 14, D-G), 

 Rhizochloris Pascher (Fig. 4. 14, A-C) and the loricate Stipitococcus 

 West and West (Fig. 4. 14, H) are included. The dominant stage in 

 Rhizochloris arachnoides is a small amoeba with slender pseudopodia 

 and a number of chromatophores. An amoeboid plasmodium also has 

 been observed. The flagellate stage apparently has only one flagellum. 

 The vegetative stage of Myxochloris sphagnicola (213) is a plasmodium 



