28 



EXPERIMENTAL GENERAL PHYSIOLOGY 



III. PROTOZOA OR ONE-CELLED ANIMALS. 



We come now to an entirely different order of beings the 

 protozoa, or one-celled animals. They live in the water and feed 

 upon unicellular plants. They sometimes contain granules of 

 chlorophyll, sufficient in quantity to give them the appearance of 

 motile plants, but the chlorophyll has been taken up with the plants 

 which they have eaten. Chlorophyll thus absorbed is retained only 

 a short time and is then excreted. The protozoa are classified as 

 follows : 



FIG. 7 





Amceba. a, at rest ; 6, extending pseudopodia in search of food; c, food enclosed; d, repro- 

 duction by fission, beginning with division of nucleus and vacuole; e, cytoplasm dividing; 

 /, reproduction complete. 



Protozoa. One-celled animals. 



1. Rhizopoda, protozoa possessing bodies of changeable shape. 



(a) Helizoa, naked rhizopoda. Ex. amoeba (Fig. 7). 



(b) Foraminifera, marine rhizopoda with porous shells. 



(c) Radiolaria, marine rhizopoda with concentric spherical 



shells. 



2. Infusoria, protozoa possessing bodies of fixed shape. 



(a) Flagellata, infusoria that swim with a whip-like flagellum. 



Ex. Euglena (Fig. 8). 



(b) Ciliata, ciliated infusoria with mouth and anus. Ex. Para- 



mcecium (Fig. 9). Vorticella (Fig. 10). 



Laboratory Exercises. 



1. Appliances. Microscope with j-inch to ^-inch objective; cell 

 slides; covers; aquaria well stocked with protozoa; drop-tubes; filter 



