PROTOZOA IN GENERAL 



79 



Flaqellum 



-Mouth 



Reservoir- 



¥ 



'Stigma 



■ Contractile 

 vacuole 



\(lhromatophorz 



4. Infusoria (in fu so' ri a; L., infusus, poured into, crowded), or 

 Ciliata (sil i a' ta). — Have a very large number of permanent small hair- 

 like appendages known as cilia. 



By some authorities a fifth class is recognized which is called Suctoria. 

 In the classification adopted here this is considered a subclass of the 

 Infusoria. 



108. Mastigophora. — A type of this class is the euglena (Fig. 29), 

 a small greenish protozoan living in bodies of fresh water. This animal 

 agrees with the Paramecium in possessing, in addition to the ectoplasm 

 and endoplasm, an elastic cuticle, which is 

 striated. On the anterior end is a single 

 long slender flagellum connected with a 

 granule within the body known as a hleph- 

 aroplast. This term is applied to any 

 granule in a cell with which a cilium or 

 flagellum is connected. The mouth is at the 

 base of the flagellum. A permanent vesicle, 

 the reservoir, into which several contractile 

 vacuoles pour their contents, opens into the 

 gullet. Close to the reservoir is a mass of 

 red coloring matter called the stigma, or 

 eyespot. It is, of course, not an organ of 

 sight, though it is thought to be sensitive 

 to light. Near the center of the body is a 

 nucleus, and scattered through the protoplasm 

 are many bodies of bright green color called 

 chromatophores. 



Euglena is a type which possesses some 

 of the characteristics of plants. Other 

 members of this class show these to such a 

 degree that they are by botanists considered 

 plants and classified by them as such. 

 A plantlike characteristic is the abihty, by means of chlorophyll in the 

 chromatophores, to manufacture part of its own food. This type of 

 nutrition is known as holophytic, in contrast with the type which char- 

 acterizes animals generally, which involves the ingestion of solid particles 

 of organic food, and which is called holozoic. This resemblance to plants 

 justifies their being considered the first class of the Protozoa. Many 

 zoologists place Sarcodina first, believing them the simplest structurally. 



Euglena illustrates particularly well a reaction to an optimum stimu- 

 lus. When placed in a vessel, one end of which is Hghted and the other 

 darkened, the animals gather neither at the light nor at the dark end 

 but in a zone between the two where the optimum of light for this animal 

 is found. 



Nucleus 



Fig. 29. — Euglena viridia 

 Ehrenberg. {Slightly modified, 

 from Doflein, "Lehrbuch der 

 Protozoenkunde," by the courtesy 

 of Gustav Fischer.) X 800. 



