74 PROTOPLASM AND THE AMCEBA. PROTOCOCCUS 



in both being isolated, independent, free-living organ- 

 isms, each consisting essentially of cytoplasm with 

 nucleus. But they show the following differences : 



(1) Amceba has no cell wall, while Protococcus has. 



(2) Amaba moves from place to place, while Pro- 

 tococcus is stationary. 



(3) Amceba feeds on living prey, while Protococcus 

 does not, having no means of ingesting solid bodies. 



On the other hand 



(4) Protococcus has part of its cell protoplasm coloured 

 green (chloroplast), which enables it to form organic 

 substance, and eventually protoplasm, from liquid and 

 gaseous inorganic substances which it can absorb 

 through its cell wall. Amceba has no such power 

 because it has no chloroplast. 



PRACTICAL WORK. 



A. AMCEBA AS A TYPE OF SIMPLE ANIMAL. 



(i) Place a drop of water containing the scrapings of the 

 surface mud of a pond containing amcebae (together with other 

 organisms and organic debris) in the centre of a slide and cover 

 with a coverslip. Examine first with the low power, and pick 

 out the amcebae, which appear as irregular blobs of greyish or 

 brownish appearance. They will gradually creep out from the 

 debris along the surface of the slide or coverslip. 



Examine a specimen with the high power and notice that it 

 is constantly changing its shape, sometimes slowly and sometimes 

 rapidly. Distinguish the clear ectoplasm from the granular 

 endoplasm, and note that the granules of the latter are very 

 various in size and shape. The endoplasm may include quite 

 large remains of ingested prey, e.g. the cell walls and disintegrated 

 contents of unicellular plants. Note also the transient projections 

 of the body (pseudopodia). 



Identify the contractile vacuole, and watch it contracting and 

 quickly reappearing at full size. Identify also the rounded, 

 granular, light-refracting nucleus. Measure the average diameter 

 of the amoeba and the diameter of the nucleus with the eye-piece 

 micrometer. 



