PHYLUM PROTOZOA 



75 



(Pliytoflagellata). The mouthless body is surrounded by a cellulose 

 cell-wall (c.w.), and contains chromatophores (chr.) coloured either 

 green by chlorophyll or red by hsematochrome. Nutrition is purely 

 holophytic, i.e. takes place by the absorption of a watery solution of 

 mineral salts and by the decomposition of carbon dioxide. It is, 

 therefore, not surprising that these chlorophyll-containing Flagellata 

 are often included among the Algae or lower green plants. 



Other genera live in a purely animal fashion by the ingestion of 

 solid proteinaceous food, usually in the form of minute living 

 organisms : in these cases there is always some contrivance for 

 capturing and swallowing the prey. In Oikomonas (Fig. 53, 8) 

 we have one of the simplest arrangements : near the base of the 

 flagellum is a slight 

 projection contain- 

 ing a vacuole (v.i.) ; 

 the movements of 

 the flagellum drive 

 small particles (/.) 

 against this region, 

 where the proto- 

 plasm is very thin 

 and readily allows 

 the particles to 

 penetrate into the 

 vacuole, where they 

 are digested. In 

 Euglena, as we 

 have seen, there is 

 a short, narrow 

 gullet, and in some 

 genera (9, g) this 

 tube becomes a 

 large and well- 

 marked structure. 



Skeleton. - 

 While a large pro- 

 portion of genera 

 are naked or covered 

 only by a thin cuticle, a few fabricate for themselves a delicate 

 chitinoid shell, or lorica (10, I.), usually vase-shaped and widely 

 open at one end so as to allow of the protrusion of the con- 

 tained animalcule. In most of the chlorophyll-containing forms 

 there is a closed cell- wall of cellulose (Fig. 55, c.w.). One group of 

 marine Flagellates (Silicoflagellata) have siliceous skeletons similar 

 to those of the Radiolaria, with which they were originally classed. 



In many genera colonies of various forms are produced by 

 repeated budding. Some of these are singularly like a zoophyte 



c.vat 



FIG. 55. Haematococcus pluvialis. A, motile stage ; 

 B, resting stage ; C, D, two modes of fission ; E, Hcemato- 

 coccus lacustris, motile stage ; F, diagram of movements of 

 flagellum ; chr. chromatophores ; c. vac. contractile 

 vacuole ; c.w. cell-wall ; nu. nucleus ; nu'. nucleolus ; 

 pyr. pyrenoids. (From Parker's Biology.) 



