The female is viviparous, and the young, which, unlike the parent, are provided with a long tail, live free in water; it was formerly believed from the frequency with which the legs and feet were attacked by this parasite that the embryo entered the skin directly from the water, but it has been shown by Fedschenko, and confirmed by Manson, Leiper and others, that the larva bores its way into the body of a Cyclops and there undergoes further development.
Ten years later Manson discovered a second species, Filaria perstans, whose larvae live in the blood.
These and other experiments, described by Dr Manson in the Practitioner for March 1900, confirming the laboratory evidence as they do, leave no doubt whatever of the correctness of the mosquito-parasitic theory of malaria.
In the tropics "no European house should be located nearer to a native village than half a mile" (Manson), and, since children are almost universally infected, "the presence of young natives in the house should be absolutely interdicted" (Manson).
Manson recommends five to ten grains once or twice a week; Ross recommends the same quantity every day before breakfast.