AlVKEBA. 



Amoebae are often found amongst the deposits of fresh water pools. When a 

 small quantity of the material containing AmoBbse is introduced into a small glass 

 aquarium, and some fresh water added, a thin film usually appears on the surface 

 of the water. This film, when examined, will be found to be composed chiefly of 

 small organisms, some of which are likely to be amoebae. 



Take by means of a pipette a small portion of the film, and allow a drop to fall 

 on a glass slide. Lay a narrow strip of moistened writing paper near to the drop, 

 and apply a covering glass so that one edge rests on the paper. Look for an Amoeba 

 with a low power, and then examine with a high power, noting that it consists of 

 an irregular shaped central portion from which blunt processes (pseudopodia) of 

 various sizes, project, and that when active the form of the body and processes are 

 constantly changing. 



A. Observe — 



1. That the body consists of — 



(a) A central mass of granular protoplasm (endosarc) which extends into 

 some of the pseudopodia, and usually contains a nucleus, a con- 

 tractile vacuole, and food particles. 



(6) A thin almost transparent outer film (ectosarc) which contains few 

 granules. 



2. The change in form, the appearance and disappearance of the pseudopodia, 



and the movements of the granules. Note that the pseudopodia seem at 

 first to consist only of ectosarc, but that as some of them increase in size 

 the granular endosarc flows into them, and further that a pseudopodium 

 may throw out new processes, and then advance, dragging, and ultimately 

 completely absorbing the body and processes behind it. 



B. Draw an Amoeba at intervals of one or two minutes to show the changes of 



form, and indicate by arrows the directions of the currents of granules. 



C. Examine — 



1. The food particles, and n&te that they usually lie at first in a small 



quantity of water (food vacuole), and that the food may consist of 

 minute plants or animals, and that in addition to food there are often 

 grains of sand and other substances. Study the process of ingestion of 

 the food particles, and the expulsion of the non-nutritious particles, and 

 note that they enter or escape from any part of the surface. 



2. The contractile vacuole, if visible, and watch its pulsations. 



3. The nucleus which may be made more distinct by adding a drop of 



acetic acid to the preparation. 



D. Add to one of the drawings the nucleus, the contractile vacuole, also the food 



vacuoles, and any foreign substances which may be present. 



E. Look for encysted Amoebae and for Amoebae in process of division by transverse 

 .fission. 



