Consideration of the outbreak of fever at Morib in Selangor, Federated Malay States, impresses us with the great practical importance of obtaining an exact comparative infectivity table of the various anophelines, compiled on a comprehensive basis; it is only by accurate study of a disease and the factors responsible for it, that it can be successfully combated.

At Morib we can only rely on general considerations and conclude that the species ludlowi has been causing most of the trouble.

It would seem that the reason that hill-land malaria in Malaya, and perhaps India, is so difficult to get, rid of is because it is conveyed by mosquitoes of high infectivity and low prevalence, whereas low-land malaria can be easily allayed because it is conveyed by mosquitoes of low infectivity and high prevalence. It is a corollary to this that if malaria in any community can be easily allayed, it is caused by mosquitoes which possess low infectivity.