7$ ELEMENTARY ZOOLOGY 



Form of body. The Protozoa all agree in having the 

 body composed for its whole lifetime of a single cell,* 

 but they differ much in shape and appearance. Some of 

 them are of the general shape and character of Amoeba, 

 sending out and retracting blunt, finger-like pseudopodia, 

 the body-mass itself having no fixed form or outline but 



FIG. 9. Sun animalcule, a fresh-water protozoan with a siliceous skeleton, 

 and long thread-like protoplasmic prolongations. (From life.) 



constantly changing. Others have the body of definite 

 form, spherical, elliptical, or flattened, enclosed by a thin 

 cuticle, and having a definite number of fine thread-like 

 or hair-like protoplasmic prolongations called flagella or 



* In some Protozoa a number of similar cells temporarily unite to form a 

 colony, but each cell may still be regarded as an individual animal. 



