CHAPTER 5 



ZOOFLAGELLATES 



The Class Zooflagellatea as presently recognized is a polyphyletic 

 assemblage of protozoa whose chief common characters are the 

 presence of flagella in vegetative stages and the absence of a clear 

 and direct relationship with phytoflagellate groups. Numbers of 

 puzzling genera have in recent years been removed from the 

 Zooflagellatea and more realistically classified as unpigmented 

 derivatives of photosynthetic forms, and some others appear to 

 be candidates for such a transfer. Many zooflagellates show 

 pronounced ameboid tendencies, and as we have noted, very many 

 rhizopods and actinopods have flagellated developmental stages, 

 so that no natural boundary separates these large groups. Grasse 

 (1952) divides the Class Zooflagellatea into three superorders: the 

 Protomonadica, a heterogeneous assortment of small uni- and 

 bi-flagellates ; the Metamonadica, consisting of seven orders of 

 multiflagellates ; and the Opalinica, an enigmatic group of intestinal 

 symbiotes of cold-blooded vertebrates, often considered to be 

 allied to the ciliates. 



Superorder Protomonadica 



The Order Choanoflagellida is a relatively small group of 

 free-living species, characterized by the possession of a delicate 

 protoplasmic collar or funnel around the base of the presumably 

 single flagellum. They may attach to a substratum by a posterior 

 peduncle, and often occupy a delicate hyaline or a silicified 

 envelope. Several features suggesting a relationship with the 

 chrysomonads are discussed by Hollande (1952b), who nonetheless 

 feels that evidence is not sufficient to justify their classification 

 with the phytoflagellates. Hollande, however, was not aware of 

 a description by Lackey (1940) of Stylochro??wnas minuta, a 

 chloroplast-containing chrysomonad with a protoplasmic collar 

 surrounding the base of the single visible flagellum. Choano- 



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