SPOROZOA 



441 



development takes place when the blood is taken into the stomach 

 of a mosquito of the genus Anopheles. Here the microgametes, 

 slender actively motile threads, are given off by the microgam- 

 etocyte and fertilize the macrogametes, producing ookinetes, 



which actively penetrate the epithelium. 

 In the wall of the mosquito's stomach 

 's~JJ\l\ W each ookinete gives rise to a rapidly 

 growing cyst and within this an enor- 

 mous number of very slender sporo- 

 zoits are developed. The rips^ cyst 

 sh " #3 \l bursts into the body cavity and the 

 sporozoits become generally distributed 

 throughout the body of the insect and < 

 later assemble in the secreting cells of 



Fig. 203. — -Digestive tract 

 of Anopheles, the stomacji of 

 which is covered with numer- 

 ous oocysts of PI. falciparum, 

 viewed from the left side, c. 

 Cloaca; o, stomach; o, oocysts 

 of Plasmodium; mt, malpighian 

 tubules; sb, sucking bladders; 

 sg, salivary gland. (From Do- 

 ftein, modified after Ross and 

 Grassi.) 



Pig. 204. — Plasmodium falciparum. 

 Ripe sporozoits arranged about r.esidual 

 bodies within the oocyst, cut in various 

 directions (7 to 8 days after infection of 

 the mosquito), (from Doflein after 

 Grassi.) 



