358 



The male trypanosome is much smaller than the other two 

 forms, but has a more fully-developed locomotor apparatus. 

 The blepharoplast is relatively much larger, and the flagellum 

 is longer, they are consequently very actively motile. 



B. Development in the mosquito. 



They do not develop further. They only become functional 

 -when they leave the blood and fertilize the female in the 

 mosquito's stomach. 



C. Development in the blood. 



As the males rapidly die out in the stomach it is not often 

 that they reach the blood. If they do they probably die quickly. 

 The mikrogametocytes of the blood are developed from the in- 

 different trypanosomes. 



The fertilization of the makrogamete (female trypanosome) 

 by the mikrogamete (male trypanosome) takes place when blood 

 is sucked into the mosquito's stomach, and thus the cycle is 

 completed. 

 The circulation of the trypanosomes in the mosquito. 



1. The gametes in the blood of the owl are sucked in. 

 The formation of the ookinet, and development into trypano- 

 somes takes place in the mid-gut in about twenty-four hours, 



2. If no more blood is given the parasites (female) are 

 now found in the resting (gregarine) stage attached to the mid- 

 gut, and they may occur in such quantity as to kill the 

 mosquito. 



3. If a second meal of blood is given development into 

 the motile stage occurs, followed by the resting stage. The 

 parasites are now collected in enormous masses (thousands) 

 around the proventriculus and commencement of the mid- gut. 



4. If a third meal of blood is given these masses are 

 washed onwards by the entering blood, eventually reach the 

 ileum and the great upward curvature of the colon. 



5. Here they penetrate the epithelium, reach the blood 

 stream, passing some backwards to the ovaries, some forwards 

 until they reach the blood spaces surrounding the pharyngeal 

 pump. They accumulate here in such masses that they even- 

 tually pass through the epithelium of the pharynx and so reach 

 the lumen. 



6. They are then washed out when the contents of the 

 diverticula, carbonic acid gas, bacteria, etc., are ejected prior 

 to the sucking act. 



7. The parasites that reach the ovaries develop there, and 

 so can be transmitted through, the larval stages to the newly- 

 hatched mosquito. 



