MORPHOLOGY AND TAXONOMY OF MASTIGOPHORA 261 



In a number of different types the monads lose their chlorophyll 

 and stigmata and, like colorless flagellates, live as saprophytes or 

 by strictly holozoic means. Pascher, Doflein, Franz and others 

 regard such forms as illustrating the probable mode of origin of the 

 Zoomastigoda. 



Encystment and reproduction within the cyst is characteristic 

 of the group the cysts being unique amongst the flagellates in 

 having silicious walls. In rare cases, apparently, does the proto- 

 plasm of the monad retract from the membrane which then becomes 

 the cyst wall. A more frequent method, according to Scherffel 

 (1911) is the formation of a hollow shell within the ectoplasm of the 

 monad, the shell being entirely closed save for a pore at one pole. 

 The ectoplasm, after variously sculpturing the outer surface of the 

 shell, retires into the pore which is then closed with a silicious stopper 

 (Fig. 5, p. 24). Comparatively few types, however, have been 

 examined and the prevalence of this peculiar method of cyst forma- 

 tion remains to be demonstrated. Within the cyst the monad 

 divides to form two or more spores the germination of which has 

 been observed. 



The sub-orders of the group, according to Pascher's classification, 

 are decidedly artificial, being based upon the relative importance 

 of the Palmella-stage in the life history. In the Euchrysomonadina 

 the Palmella-stage is temporary and facultative and the flagella- 

 bearing or motile stage is dominant. In the Chrysocapsina the 

 motile stage is temporary and the Palmella-stage dominant, and in 

 the Rhizochrysidina the flagellum-bearing phase has never been 

 observed, the organisms being placed here rather than with the 

 Sarcodina because of their yellow-brown chromatophores and 

 products of metabolism. 



Sub-order I. Euchrysomonadina. 



Yellow or brown monads with one or two flagella which may be 

 discarded from time to time, pseudopodia taking their place. In 

 some forms the pseudopodia stage represents the fully grown or 

 mature phase of the organism. We recognize five families, three 

 of which— Clu-omulinidse, Isochrysidae, and OchromonadidfE— are 

 represented mainly by fresh-water forms; but investigation will 

 probably show that there are as many salt-water forms. Two 

 families— Silicoflagellidse and Coccolithophorida?— are exclusively 

 marine. 



Family l.—Chromulinidse.— Usually minute forms with a single 

 apical flagellum; solitary for the most part, colony forms rare 

 (one genus, ChrysosphcBreUa) . They may be either free-swimming 

 or attached, naked or covered by a shell. Pseudopodia formation 



