204 



BIOLOGY OF THE PROTOZOA 



of a simple skeleton of silica in the form of a ring {Mesocena, Lemm.) 

 or of a ring with bars. Distei)hanus.specidum, Ehr, is associated with 

 Radiolaria as a parasite or a symbiont. It has a single flagellum, 

 yellow chromatophores and a fenestrated silicious skeleton. Little is 

 known about its life history and at one time it was supposed to be 

 a stage in the development of certain forms of Radiolaria (Fig. 128). 



A 



B 



Fig. 128. 



-Distephanus sTpeculum, side {A) and top (S) views of skeleton. 

 Calkins after Borgert.) 



(From 



Sub-order 2. Rhizochrysidina, Pascher. 



A highly artificial group consisting of genera in which no flagella 

 have been described but which move by means of pseudopodia. The 

 temporary nature of the group is indicated by the fact that as soon 

 as a flagellum is observed in any member of the sub-division, that 

 species becomes one of the Euchrysomonadina. It is retained in 

 the classification merely for convenience in holding pseudopodia- 

 bearing forms with yellow chromatophores and no flagella. The 

 genera Rhizochrysis, Chrysidiastrum and Chrysostephanosphaera are 

 naked, while Stylococcus and Lagynion are test-dwelling with long, 

 thread-like, often single, pseudopodia. 



Sub-order 3. Chrysocapsina, Pascher. 



While Palmella stages are characteristic of all the Chrysomonadida 

 in this group they become the prevailing stage and flagellated forms 

 are transitory. Here the individuals are enclosed in a gelatinous 



