154 



GENERAL BIOLOGY OF MICRO-ORGANISMS 



in a sheath of ectoplasm, which is drawn out into a thin sheet 

 forming an undulating membrane. Multiplication takes place 

 by approximately longitudinal division. Leishmania includes a 

 few parasitic forms, for the most part living inside the cells of 

 the host. These organisms are oval, about 2X3^, without fla- 

 gellum or undulating membrane. In artificial culture outside 

 the body, the protozoon grows larger, develops a flagellum and 

 resembles a trypanosome. Trichomonas includes pear-shaped 



F G H I 



FIG. 77. Entamceba coli (Losch). A to C, Various forms of the free ameba. 

 D, Stage with eight nuclei. to G, Cysts with various numbers of nuclei. H, 

 Opening cyst. 1, Young amebae escaped from a c>st. (From Doflein after Casa- 

 grandi and Barbagallo.) 



organisms 4 to 30/4 in diameter, provided with three or four fla- 

 gella. Isogamic and autogamic fertilization have been described, 

 and cysts containing numerous daughter cells result from the 

 multiplication following this process. Lamblia resembles tricho- 

 monas, but the cell is here shaped more like a beet, is provided 

 with eight flagella and is hollowed out at one side near the 

 rounded anterior end to form a suction cavity. 



Rhizopods. The members of the second class, Rhizopoda, 

 are characterized by their ability to send out protoplasmic proc- 



