One of the greatest difficulties of anti-mosquito work in Palestine is that there are a series of swamps in the littoral plain, lying almost at sea level and prevented from draining into the Mediterranean by sand-dunes and sand-bars which block their outlet channels. It appears that cutting channels through the coastal dunes is a task which would have to be repeated at very frequent intervals, and until some-what large sums of money are available the pumping of these numerous swamps into the sea cannot be undertaken. There are, moreover, other rather large areas of marsh, notably Lake Huleh, Beisan marsh and the Marj Sanour, the proper drainage of which is at the moment beyond the financial resources of the country. We have therefore to rely for the moment on ameliorative measures which are admittedly not sufficiently radical. Among other things, I have begun a study of our native fish, hoping to find some small and voracious species that breeds rapidly and is able to live in waters of different degrees of salinity. The results which I have obtained are perhaps discouraging, but certainly interesting.