286 



ESSENTIALS OF ZOOLOGY 



some simpler and some more complex than Amoeba proteus. Chaos 

 diffluens is a very desirable species for study. Recently Chaos chaos 

 Schaeffer has been rediscovered. It is enormous in size and can be 

 seen with the unaided eye. 



Characteristics and Habitat 



The many kinds of Amoeba live in fresh water, marine water, 

 soil, or as parasites in the fluids of the visceral organs of higher 

 types of animals. Amoeba proteus may be collected in a variety of 

 places where conditions of water, temperature, and organic food 

 are favorable, such as debris from watering troughs, bottoms of 

 ponds, spring pools, drain ditches, abandoned tanning pits, in streams 

 where the water runs over rocky ledges, and wherever there is abun- 

 dant aquatic vegetation. It is often found on the surface of sub- 

 merged lily pads. A mass of pond weed may be brought into the 



rooo 



VACUOL.E 

 CONTRACTIL-E 

 VACUOL- E 



NUCL.EUS 



ENOOPL,ASM 



^ PSEUDO PODIUM 



ECTOPL-ASM 



Fig. 94. — The structure and appearance of living Amoeba proteus. 



laboratory in some of the pond water and allowed to stand in the 

 container a few days. If amoebae are present, they will likely be in 

 the brown scum which forms, or in the sediment at the bottom. 



The general appearance of this animal is that of a slate-colored, 

 lustrous, irregular mass of gelatinlike substance with slowly-moving, 

 fine particles within. When it is active, the outline is constantly 

 changing. 



Structure 



Amoeba proteus is one of the largest of the fresh-water forms. 

 Its average diameter is about %oo inch (0.25 mm.), while its ex- 

 treme diameter is %o inch or barely visible as little specks to the 

 unaided human eye. The animal owes its irregular shape to the fact 

 that protrusions of its own substance are formed at its surface. 



