CHAPTER VI 



AMCEBA 



Amceba proteus is a little organism found in the mud 

 and on weeds in freshwater ponds. A large 

 Features. specimen is just visible to the naked eye as a 

 minute, irregular, whitish speck. Under the 

 microscope (with transmitted light) this is seen to be a mass 

 of translucent slime, greyish in colour owing to the presence 

 of numerous small, dark granules. The outer layer is clear 

 and transparent owing to the absence of the granules. This 

 layer is called the ectoplasm, the granular inner part being 

 the endoplasm. In the endoplasm are usually to be seen 

 the remains of other little organisms, especially the brownish 

 plants known as diatoms, which form the food of Amoeba. 

 At one spot is a round space filled with a clear fluid, which 

 grows gradually larger and then suddenly disappears, owing 

 to a contraction of the protoplasm around it causing it to 

 burst out and discharge its contents into the surrounding 

 water. It then gradually re-forms in the same portion of 

 protoplasm as before. This space is called the contractile 

 vacuole. There are usually other small vacuoles which are not 

 contractile. With care there may also be seen in the living 

 specimen a lens-shaped body of moderate size which is 

 somewhat denser than the rest of the protoplasm. This is 

 the nucleus. If the animal be killed and stained with 

 carmine or any of a number of other dyes, the nucleus 

 takes up the stain more deeply than the cytoplasm. The 

 irregular shape of the body is constantly changing, owing 

 to the outgrowth of new processes or pseudopodia and the 

 withdrawal of old ones. 

 8 



