and zygotes in mosquitos infected with malaria. 7 



Problems concerning the Infsoction of Mosquitos which neee 

 FURTHER Investigation. 



1. Bodies of uncertain significance found in the Salivary Glands of 

 various Mosquitos. 



(a.) In a large Auoplieliue {Myzorhijiichus '^ up.), a species not frequenting 

 houses, caught in tlie bush in Sierra Ijeone at a considerable distance from 

 human habitations, sporozoits were found in one out of four examined. The 

 nature of these is unknown, and further observations are much needed. 



(J.) The examination of specimens of an undetermined species of Cnlex at 

 Mabang, Sierra Leone, showed that 10 per cent, contained bodies resembling 

 sporozoits, but more slender, twisted and irregular in outline. Some of these 

 Culicines had fed on human blood, others were caught in the bush. Here again 

 we have no knowledge as to the nature of these bodies. 



(c.) In another undetermined Gidex, 5 to 10 per cent, of the specimens 

 contained straight bodies in the globules of salivary secretion. These resembled 

 sporozoits, but were probably crystalline in nature. 



2. Alleged transmission of Malarial Infection through the Eggs of the 

 Mosquito. — Statements have been made, without a vestige of proof, that such 

 transmission occurs. It may be well, therefore, to examine the eggs of 

 Anophelines for sporozoits. Even should infected eggs be found, it would not 

 be clear how they could transmit infection to the adult mosquito hatched from 

 them, as there is no evidence that the sporozoits multiply or undergo further 

 development in the mosquito. If we suppose that hereditary transmission does 

 occur, the form of the parasite may be quite different from anything we know. 

 Hence the study of the contents of normal eggs is of importance. 



3. What are the conditions which determine successful infection of 

 Anophelines fed on malarial blood ? — In feeding experiments only a certain 

 percentage ai-e as a rule successful. In experiments made by Christophers and 

 myself in India we got no result until we kept the Anophelines in a hot 

 incubator, though in the villages they were naturally infected. Is it quite 

 certain that no Culicines can transmit malaria ? 



4. How many persons can one Anopheline infect ?— We have no data on 

 this point. lu the case of Culicines the brothers Sergent have shewn that an 

 infected Culicine can infect two, but not three consecutive birds with Proteosomu. 

 Similar experiments might be made in the case of Anophelines and man, but in 

 case this is not possible the experiments should be made with Culicine sporozoits 

 on birds ; and, indeed, if opportunity otters, bird-malaria still affords a fruitful 

 field of research. In the greater part of Africa, however, Proteosoma does not 

 exist, but in the mode of transmission of Halteridium, Haemogregarines, &c., 

 there is abimdance of work to be done. 



4. Does the percentage of infected Anophelines vary from month to 

 month, and if so, to what extent ? 



5. How long does an Anopheline once infected remain so ? 



