THE ANIMAL KINGDOM 



371 



water in a narrow glass chamber which is mounted on the 

 stage of a microscope, tilted into a horizontal position. In 

 this position the bottom of the chamber is horizontal and the 

 amoeba can then be watched as it moves over the bottom to 

 the observer's right or left. Under these conditions it can 



Fig. 205. — Amoeba proteus with pseudopodia extended. EC, ectoplasm; 

 en, endoplasm; f.v., food vacuole; c.v., contractile vacuole, expanded; n, 

 nucleus. 



be determined that the amoeba moves by extending and 

 attaching a pseudopodium to the bottom and then drawing the 

 rest of the body toward the attached pseudopodium (Fig. 206). 

 The nucleus has a rounded outline but is not unalterably 

 fixed in position in the cytoplasm. Two general regions are 



Fig. 206. — Side view of Amoeba proteus moving over a solid substratum by 

 attaching the extended pseudopodia and then drawing itself forward. (Adapted 

 from Dellinger, Jour. Exp. Zool.) 



recognized in the cytoplasm: an inner portion, the endosarc 

 or endoplasm, and an outer bounding layer, the ectosarc or 

 ectoplasm. The endoplasm, in which the nucleus is located, 

 has a granular appearance caused by the presence of embedded 

 particles of various sizes, some of them food particles, others 



