MALARIA IN GENERAL 351 



What factors bring about these differences in distribution, etc., and 

 what are their relations to virulence, latency, relapse, etc. ? 



(2) Is the malarial parasite inside or outside of the red cell? 

 In all stages? Do the parasites migrate from one cell to another? 

 (Lawson, 1920; Ratcliffe, 1927.) 



(3) Is there a filterable stage in the life-cycle, especially during 

 the period between relapses when no parasites can be found in 

 the peripheral blood? (Boyd, 1925.) 



(4) When and where does the change take place from schizonts 

 to gametocytes? Factors? Does the sex of the host have any 

 influence on the production and sex of the gametoc\i:es ? 



(5) Does treatment with quinine increase the number of game- 

 tocytes? (Clark, 1928.) 



b. Life-cycle of malaria parasites in mosquitoes. 



(i) In nature, what is the influence of temperature, moisture, 

 latitude and altitude on sporogony in the mosquito? On the length 

 of different stages? On the numbers of oocysts? On the numbers 

 and distribution of sporozoites ? Does the environment of the 

 mosquito or its larva or pupa have any eft'ect on its infectivity? 

 Humidity, temperature, salinity of water, food, altitude? 



(2) What effects do starvation, various diets, etc., have on 

 stages in the life-cycle in mosquitoes? Duration of stages? Num- 

 bers ? Length of infectivity ? 



(3) Are stages in sporogony as worked out by Grassi (1901) 

 correct ? 



(4) Are different species of mosquitoes responsible for the ap- 

 pearance of P. vivax early and P. falciparum later in the season? 

 Are mosquitoes responsible for the local appearance of malaria? 

 Plasmodium malarice may be abundant in a spot surrounded by 

 P. vivax and P. falciparum but free from P. malarice. 



(5) Do mosquitoes suft'er from infection? Do non-infected 

 mosquitoes live longer than infected mosquitoes? 



(6) What effects do hibernation and estivation have on 

 sporogony ? 



(7) How many gametocytes are necessary to infect mosquitoes? 

 (Darling, 1910.) 



(8) How many oocysts are necessary to produce an infective 

 mosquito? 



(9) There are various degrees of susceptibility among mosquito 

 hosts. Why is there not infection in all hospitable hosts ? 



