144 
Malaria in Ceylon 
order to fill them, and thus cannot flow by force of gravity alone. On 
subsiding, the water leaves stagnant pools behind, in which larvae are 
to be found. This is especially so in the case of the channel situated 
behind the station {vide PI. XI, fig. 7). 
(4) Rock Pool (PI. VIII, fig. 2). This is a rainwater pool, which 
has collected in a disused quarry. Great numbers of larvae can nearly 
always be found there, though their numbers have been somewhat 
lessened by the introduction of fish by Gunasekara. 
(5) Borrow Pits (PI. XIII, fig. 11). Many of these have been 
excavated by the Public Works Department during their work on the 
Circular Road in the south of the town ; formerly they used to be fertile c 
breeding grounds of anophelines. The majority have been dealt with 
under Gunasekara’s directions ; as a focus of malarial infection they 
may now be almost disregarded. 
(6) Freshwater Wells. According to Gunasekara there are 180 
town wells ; in only 18 of these were a few larvae found. Larvivorous 
fish have now been introduced, so that as centres of infection they, too, 
may be disregarded. One well supplies some blocks of paddy fields on 
the Rajaphilla road ; these are nearly always under water, and larvae 
can always be found there (PI. X, fig. 5). 
(7) Rock Stream (PL IX, fig. 3). This stream flows behind the 
Government Agent’s residence; in the dry season it is represented by a 
series of stagnant pools. From larvae captured there, M. barbirostris and 
one specimen of M. maculatus {vel wilmori) have been bred. Reference 
must here be made to a practice of the villagers of damming up this 
stream to form a bath for their bulls, thus creating large stagnant 
pools ; this practice also ought to be forbidden. 
(8) Water Channels on each side of Railway Cutting (PI. XII, fig. 8). 
This water supplies the engines at the station. The courses are only 
cemented underneath the bridge, and are not kept clean', the result is that 
they are overgrown with slimy water plants ( spirogyra ), which form an 
excellent feeding ground for larvae, and to which they adhere by their 
tails. This stream, and the presence of continually flooded paddy fields 
in the vicinity, probably account for much of the malaria amongst the 
railway staff for which the station at Ivurunegala has an invidious 
reputation. There is no reason why this reproach to the Railway De¬ 
partment should not be removed, and increased efficiency result. The 
following list will give an idea of the importance of these various sheets 
of water in breeding malaria-conveying anophelines. Malaria carriers 
are printed in heavy type : 
