20 



Insects and Disease 



velopment as did the parent form. This process 

 of growth and division may go on for many gener- 

 ations, but cannot continue indefinitely unless there 

 is a conjugation of two separate individuals. This 

 process of conjugation is just the opposite to that 

 of division. Two amoeba flow together and be- 

 come one. It seems to rejuvenate the organism so 

 that it is able to go on with its division and thus 

 fulfil its life-mission which is the same for these 

 lowly animals as with the higher, that of perpetu- 

 ating the species. 



Classes o] Protozoa. The group or Phylum Pro- 

 tozoa is divided into four smaller groups or classes. 

 The amoeba belongs to the lowest of these, the 

 Rhizopoda. Rhizopoda means "root-footed," and 

 the name is applied to these animals because most 

 of them move about by means of root-like processes 

 known as pseudopodia or " false feet." This is 

 by far the largest class and contains thousands of 

 forms, mostly living in salt water but there are 

 many fresh-water species. They are non-parasitic, 

 but some of them by their presence in the body 

 may cause such diseases as dysentery, etc. 



The next class which may be known as the whip- 

 bearers (Mastigophora) includes those Protozoa 

 that move by fine undulating processes called 

 flagella. One of the common representatives of 



