ANIMAL BIOLOGY 



they have played an important part in building up cer- 

 tain deposits of the earth's crust; but most important of 



FIG. 123. Life history of the malarial parasite. I, sporozoit as it 

 enters the blood from the bite of a mosquito. This sporozoit becomes 

 an amoeboid body, 2, which enters a red blood corpuscle and grows, 

 3-5; 6, amoeboid bodies into which the parasite breaks up and which 

 enter new corpuscles and repeat the same history until the sexual cycle 

 appears (7-11); 7-9, female cells; ja-gb, male cells; 10, union of female 

 cell with filamentous male cell; (this occurs in the stomach of a mos- 

 quito); ii, fertilized cell; 12, the same when imbedded in the wall of the 

 stomach of the mosquito; 13-15, growth of this cell, multiplication of 

 nuclei, and breaking up of protoplasm to form numerous spindle-shaped 

 sporozoits, many of which later get into the salivary gland of the mosquito. 

 (After Schaudinn.) 



all is the role they play in the food relations of other organ- 

 isms. Protozoa devour bacteria and other simple plants ; 



