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numbers in houses to have very much effect on the amount of malaria.
A. Barbirostris and A. Sinensis are certainly " wild " species very rarely found in
houses. We have however shown that under experimental conditions the parasites
of human malaria are capable of developing in A. Barbirostris. A. Pul-
cherrimus is a rare species which cannot, I think, exercise any influence on the
amount of malaria. A. Fuliginosus is very common in houses and stables in
some districts. Under experimental conditions, we have shown that the parasite
of human malaria can develop in this species, and though we have never
found it infected in nature, it is possible that it may occasionally have some
influence. A. Maculata, A. Stephensii, A Theobaldi, A. famesii, and A. Tur-
khudi are all moderately frequent in some districts and may occasionally be
responsible for some of the malaria, though we have never found any of these
species infected in nature.

   The group of anopheles which is certainly more important than any other
from the point of view of malaria in India is the group of small brown anopheles
comprising A. Fluviatilis, A. Culicifacies and their allies. The members of this
group are the only ones that we have found infected in nature in India, and from
this fact and the fact that in places of high endemicity one or other of the members
of this group are always found to be present, while in places where there is
little or no malaria the members of this group are absent, it is almost certain that
this is by far the most important group of anopheles in India, and that in
nature its members are better malaria carriers than any other anopheles.

   II. The effect of the importation of non-immunised strangers into an immune
district, and the effect of social status on endemicity.

   Koch has shown that the importation of a number of non-immunised
individuals into an immune district may bring about an increase in the fever rate,
and that after a time the fever rate again declines as the new-comers become
immune. This might partly account for the high endemicity of the Duars where
coolies are imported for the tea plantations; but the parents of the children
examined by us in this district had for the most part lived many years on the
plantations and all the children had been born there, so that but little, if any, influ-
ence can be assigned to this cause. Moreover, no immigration occurs in many
of the other areas of high endemicity which we examined, as, for example,
at Mainaiguri in Bengal (endemic index, 25 per cent.) or at Ennur in Madras
(endemic index, 54 per cent.).

   As regards the influence of social status, children of low social status
frequently showed a high rate of malarial infection, but on the other hand there are
many instances (e.g., Calcutta, and Vizagapatam village, endemic index, 0 per
cent.), where people of very low social status showed little or no malaria, so that but
little importance attaches to this factor.