. Biology . e detected(Fig. 22). Allied Forms.—Many hundreds ofspecies of flagellated protozoa areknown and may exhibit the mostmanifold variations in structuresand functions. Many of them have only one flagellum,as Peranema or Euglena, for example, which are commonorganisms in infusions of different kinds. It is a remarkableand fascinating sight to see a relatively large cell like Pera-nema drawn steadily forward by the undulations of the tip ofits long and easily seen flagellum. In this case the entireflagellum does not vibrate, but only the tip, whereas in Euglenathe whole flagellum is in c
. Biology . e detected(Fig. 22). Allied Forms.—Many hundreds ofspecies of flagellated protozoa areknown and may exhibit the mostmanifold variations in structuresand functions. Many of them have only one flagellum,as Peranema or Euglena, for example, which are commonorganisms in infusions of different kinds. It is a remarkableand fascinating sight to see a relatively large cell like Pera-nema drawn steadily forward by the undulations of the tip ofits long and easily seen flagellum. In this case the entireflagellum does not vibrate, but only the tip, whereas in Euglenathe whole flagellum is in constant motion and almost invisible. Nutrition in Peranema, as in Chilomonas, is saprozoic, but itis entirely different in the case of Euglena which has the powerto manufacture its food in the same way that the higher greenplants do. This holophytic nutrition is accomplished throughthe agency of chloroplastids or color-bearing structures distrib-uted throughout the protoplasm of the Euglena cell (Fig. 21).. Fig. 23.—Symira iivella, acolony of flagellated proto-zoa in which the individualsare attached at a commoncenter. From a photograph. 58 ORGANISMS OF ONE CELL The color is due to a substance termed chlorophyll which, withthe aid of sunlight, is able to manufacture starch; this, in turn,is built up into protein matter which serves as food (see ChapterV). Another colored structure is also found in Euglena,although it is not so conspicuous as the green is the red-colored spot or stigma which is more sensitiveto light than other parts of the protoplasm, and is often spokenof as a rudimentary eye-spot. In many cases it is accom-panied by a lens-like body which may concentrate light rays Fig. 24.—Uroglena americana, a colony of flagellated protozoa in which the indi-viduals are embedded in a common gelatinous matrix. on a particular spot and so act as a directive agent; at anyrate this spot is usually turned toward the source of lightand it serves therefor
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