408 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XX. 



places of this sort, the species concerned in the spread of malaria 

 depend upon clean water for breeding purposes. One of the main 

 reasons why the centre of towns and cities is often comparatively 

 free of malaria is because the surface water speedily becomes too 

 foul and dirty to allow of the breeding of dangerous anopheles ; 

 but if wells and cisterns and tanks of clean water are present 

 malaria may occur and when it does so ignorant people ascribe it 

 to bad smells, decaying organic matter and impure water. 



In order to give you a clear idea of the kind of breeding places 

 that are selected by N. stephensi I will mention some of the places 

 in Bombay in which I have found the larvas of this mosquito. 

 Permanent Breeding Places. 



Among permanent collections of water I have found them most 

 frequently in wells. Out of nearly 4,000 wells they have been 

 present in about 1,200. In no case have they been found in wells 

 containing foul stinking water. 



Bombay possesses an exceedingly large number of wells, pro- 

 bably not less than 7,000. At one time these formed the sole 

 water-supply of the island, but since the introduction of a pipe 

 water-supply many of them have gone out of use and they now 

 constitute a serious danger to the health of the inhabitants. Many 

 of the wells in the older parts of the City are inside the houses. 

 These are either placed in a dark basement, where one requires a 

 lamp in order to examine them, or else below a central shaft 

 running right up through the house and either open to the sky or 

 lighted by a sky-light. Generally this central shaft is overlooked 

 by landings on each floor or else windows or doors are so arranged 

 that people can lean over and by letting down a vessel attached to a 

 rope can draw water without descending to the well mouth. No i 

 doubt this arrangement was very convenient in the old days and 

 saved people much trouble in drawing water for the upper floors oi 

 lofty houses, but it is difficult to conceive of a more ideal arrange- 

 ment for the spread of malaria when anopheles mosquitoes, capable 

 of transmitting the disease, are breeding in the wells and can find 

 access to numbers of people living on each floor of the house, which 

 is usually rge and divided into a number of different tenements. 



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