PHYLUM PROTOZOA 



33 



In addition to reproduction by simple binary fission, 

 spore-formation also occurs in some of the Radiolaria. The 

 protoplasm contained in the central capsule breaks up into 

 small masses, each of which becomes a flagellula provided 

 with a flagellum (Fig. 44, E, F). 



In most of the Radiolaria there occur in the extra-capsular 

 protoplasm minute yellow cells (Fig. 9, z), which multiply 



FIG. ii. CollOZOUm inerme. A C, three forms of the entire colony, nat. size; 

 D, a small colony showing the numerous capsules (c. caps} and extra-capsular 

 protoplasm with vacuoles (vac} ; E, spores containing crystals (c) ; mega- and 

 microspore. (From Blitschli's Protozoa, after Hertwig and Brandt.) 



independently by binary fission. It has been proved that 

 these are microscopic unicellular plants (Zooxanthella) of 

 the class Algae, which live in the substance of the protoplasm 

 of the living Radiolarian. Such an intimate association 

 between two living organisms is known as symbiosis. There 

 can be no doubt that this association is beneficial both to the 

 Radiolarian and to the Alga. It is characteristic of the 

 plant cell that under the action of light and in the presence 



