One-Celled and Many-Celled Animals 321 



her of divisions the new animals are of less size than the parent 

 and do not appear to have the same vigor. 



While this method is the common method of reproduction, 

 it sometimes happens that two cells join together for a time and 

 appear to be a single individual, after which they separate. This 

 method is called cell-union, or conjugation. 



After the two cells have separated, each appears to take on a 

 new lease of life, and the animals resulting from future divisions 

 are larger and more active. It is supposed that this increased 

 vigor is the result of the combining of the nucleus material of 

 the two cells that united. 



The Amoeba. 



1. Using a compound microscope observe a living amoeba; also 

 have available a slide containing a stained mounted specimen and 

 suitable charts. 



2. Observe the cell body, noting its glassy, jelly-like appearance. 



3. Observe the projections that constantly change. These are 

 the so-called false feet, called pseudopods. 



4. Observe the minute particles of food it contains. 



5. On the slide observe the nucleus, the denser, more deeply 

 stained part. 



6. Make a labeled drawing of the animal, indicating the vari- 

 ous parts. 



Functions of the Amoeba. 



The amoeba is an animal 

 more simple in structure than 

 the paramecium, but it per- 

 forms the same functions. food vacudes 



Sensation. - The amoeba AN AM(EBA 



gives evidence of sensation, 



although, like the paramecium, it has no sense organs. It responds 

 to the stimuli of light, heat, electricity, chemicals, and contact with 

 particles of sand or food ; in other words, it is sensitive. 



Motion. The most characteristic thing about the amoeba in 

 its active stage is its ever-changing shape caused by the move- 

 ments of the pseudopods, false feet, as they push ahead in the 

 direction the animal is going. 



