AMCEBA AND SOME ALLIES 289 



The Amoeba. The amoeba (Amoe'ba pro'teus, Fig. 150) is 

 common in stagnant water of all lands, but it is so minute 

 that it is impossible to be sure of its presence in a given 

 place until examination has been made with a compound 

 microscope. 



One of the best ways to find large specimens of the amoeba 

 is to remove carefully from the bottom of a well-stocked 

 fresh- water aquarium a few dead leaves. A medicine-dropper 



full of material from the ^ 



surface of one of the leaves ,*•>. /$&££■) 



may yield several speci- vlSftfPr'' 



mens. A short time after v^lsilf;! 



a few drops of the water fSPfe>^ -^ i : l§te 



have been mounted on a 



glass slide the amcebas will 



exhibit their characteristic 



structure and activities. 



The usual diameter of an 



amoeba is about .5 mm. Fig. 150. Amoeba. (Much enlarged) * 



(^o inch). 



Structure and Appearance. The simplest structure en- 

 countered in any living animal is that found in an amoeba. 

 Under the microscope this minute animal is seen as a drop- 

 let of practically colorless jelly-like fluid only with difficulty 

 distinguished from the water surrounding it. The granular 

 protoplasm of which this body is composed is usually in 

 motion, stretching out here and there as small lobes in- 

 creasing in size until the whole tody seems to flow along. 

 The projections which produce this movement are called 

 pseudopodia (false feet). The entire body is surrounded by 

 a very thin nongranular layer called the ectoplasm, which 

 contains within it a more fluid granular mass, the endo- 

 plasm. Part of the granular nature of the endoplasm is due 



1 From Sedgwick and Wilson's General Biology. 



