CHAPTER VIII 



THOSE of us who have had an opportunity, in studying micro- 

 scopic life in water, to observe the restless movements of the 

 tiny bits of naked protoplasm which we call amebse, having 

 watched them slowly creep along the surface of a slide, extending 

 a portion of the body as a finger-like projection or " pseudo- 

 podium " and then allowing the rest of the body to flow up to 

 the new position; having seen them creep up on tiny protozoans 

 or other single-celled organisms and devour them by merely 

 wrapping themselves around them, thus engulfing them in an 

 improvised stomach; and having seen them propagate their 

 kind by simply constricting in the middle and dividing in two; 

 those of us who have observed these acts on the part of such 

 tiny and simple animals have come to be fascinated by them and 

 to like them, and find it hard to realize that certain species are 

 :'nstrumental in causing some important human diseases. Amebse 

 are found almost everywhere in water, soil and carrion. They 

 have even been found recently to exist in large numbers in the 

 sunbaked sands of the Egyptian deserts, lying dormant in their 

 cysts which protect them from evaporation, ready to emerge 

 and resume an active life when they become moistened. In 

 view of the wide adaptability of these animals it is not surprising 

 to discover some living as parasites, finding congenial surround- 

 ings in the bodies of higher animals. 



Classification. Amebse are protozoans belonging to the sub- 

 class Sarcodina, a group characterized by a body without a 

 cuticle, though sometimes protected by a shell or cyst wall, and 

 by their peculiar method of locomotion. In the adult form they 

 have neither flagella nor cilia, but simply outgrowths of proto- 

 plasm, called pseudopodia. In the amebse and their close rela- 

 tives the pseudopodia can be projected anywhere on the surface 

 of the body, now here, now there, though the number, form and 

 activity of the pseudopodia are quite different in different species. 



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