36 



of the Radiolarians are attractive to the Zooxanthellce 

 as a rich and ready source of nutrition. They enter the 

 ectoplasm of the Radiolarian and live there permanently, 

 consuming the nitrogen and carbon dioxide and supplying 

 free oxygen and starclu Protected by their cellulose coats 

 they are able to resist the digestive ferment of their host, 

 until degeneration of the nuclei (through repeated re- 

 production by fission) weakens their coats, and then 

 many of them become food for their host. After their 

 entrance, the Radiolarian ceases to prey on Infusorians, 

 etc., and no longer ingests solid food ; it relies on its re- 

 serves and on the Zooxanthellce. When the endoplasm of 

 the Radiolarian is broken up for sporulation, the dying 

 ectoplasm is used by the Zooxanthellce, which then divide 

 up into free-living spores which begin a new free life. 



The partnership would appear to be one of mutual 

 advantage (symbiosis) ; but it is ra'ther one in which the 

 Radiolarian is predominant, ultimately becoming . para- 

 sitic on the Zooxanthellse. 



CLASS FLAGELLATA, OR MASTIGOPHORA. 



State the Characteristic Features of the Flagellata and name 

 some Examples. 



The body usually has a definite rind or cuticle and is 

 provided (at or near the anterior end) with one or more 

 whip-like processes or flagella for locomotion. There is 

 generally only one nucleus ; when two are present, one 

 (the kinetonucleus) is situated near the base of the flag- 

 ellum and controls its activity. Many Flagellates have 

 chromatophores containing chlorophyll, and are (holo- 

 phytic) able to utilise carbon dioxide like plants ; some 

 are (saprophytic) capable of absorbing nutrient matter in 

 solution like fungi ; others are holozoic (ingesting solid 

 food as true animals do), and several are parasitic. In 

 many instances their mode of living is both plant-like 

 and animal-like. They exhibit a varying metabolism 



