AMCEBA. 5 



III. Make a series of sketches of the outline at as short 

 inten'als as possible, to show the changes of form. 



IV. Study the gi'owth of a pseudopodium. At first it 

 is a simple transparent protrusion (Fig. 1, d) of the 

 ectosarc, looking like a drop of fluid which has been 

 squeezed out of the body. As it increases in size, the 

 granular endosarc suddenly rushes into it (Fig. 1, e). It 

 may then elongate until it forms a long, blunt, finger-like 

 process, which may remain simple for some time (Fig. 1, 6), 

 or it may branch (Fig. 1,/), by forming new pseudopo- 

 dia along its sides. Notice that, as the pseudopodium 

 grows, the endosarc flows into it with a well-marked cur- 

 rent. In this way the whole body may flow forward 

 into an advancing pseudopodium, which is thus converted 

 into the body of the organism, and may throw out new 

 pseudopodia in the same or in a difl"erent direction. Xote 

 that, while progi'essing in this manner, the organism is 

 specialized into : — 



a. An anterior progressing region, with numerous grow- 

 ing pseudopodia, and, — 



b. A posterior or " following " region, with few pseudo- 

 podia. This posterior region frequently has a well-marked, 

 rounded outline covered with small eminences, the last 

 traces of the vanishing pseudopodia. Xote that manj'^ of 

 the pseudopodia disappear or are withdrawn into the body 

 or into other pseudopodia almost immediately after they 

 become visible. • 



V. Foreign bodies contained in the endosarc : — 



a. The food vacuoles. The endosarc of most speci- 

 mens will be found to contain small, nearly spherical pel- 

 lets of food, usually of a yellowish-brown color, although 

 the color varies accordinor to the character of the food. 

 In most cases a clear, transparent space surrounds the 



