68 COLLEGE ZOOLOGY 



Such species as Euglena do not ingest solid food, but manufacture 

 it by means of chlorophyll. 



Usually some structure is present which aids in the ingestion 

 of food, but in the Rhizopoda, like Ameba, there is no mouth, 

 and food is engulfed at any point on the surface. The flagella of 

 many flagellates and the cilia of ciliates draw or drive food par- 

 ticles toward the mouth and down into the gullet at the end of 

 which a food vacuole is formed (Paramecium, Fig. 33, f. v.). The 

 Suctoria (Fig. 43, D) capture their prey with their tentacles 

 and suck the contents into the body. Parasitic Protozoa take 

 food directly through the surface of the body. 



Digestion takes place in the food vacuoles, which are really 

 temporary stomachs. The surrounding protoplasm secretes fer- 

 ments which enter the vacuoles and dissolve certain food sub- 

 stances. Undigested matter is cast out at any point (Ameba),' 

 or at a particular spot (Paramecium), or through a definite anal 

 opening (Stentor). Digested food passes out into the cytoplasm 

 and is assimilated, i.e. is transformed into protoplasm. Figure 

 6 indicates that oxygen is necessary before life activities can be 

 carried on, and carbon dioxide is given off. This is respiration. 

 The oxygen is taken in through the body- wall. It combines with 

 protoplasm, i.e. oxidation takes place. Free energy is a result 

 of this oxidation, and carbon dioxide and other waste matter in 

 solution are by-products. These by-products pass out through 

 the body-wall, and probably by way of the contractile vacuole. 

 The contractile vacuole may therefore be called a primitive 

 excretory organ. 



From the above discussion it may be concluded that the Pro- 

 tozoa carry on many of the activities characteristic of the higher 

 organisms without the aid of the systems of organs we usually 

 associate with these functions. 



Behavior. — Locomotion. — Protozoa move from place to 

 place either by creeping over the surface of objects (Ameba, Fig. 

 9; Stylonychia, Fig. 43, B), or by free swimming. The loco- 

 motor organs are pseudopodia, flagella, and cilia. In some Pro- 



