SUNIER: Marine fish-ponds of Batavia. 287 
salt-water breeding-places which makes these breeding places so suitable 
to ludlowi. 
Should this be so there would be less matter for surprise in the 
occurrence of /udlowi in the interior of Sumatra in the fresh-water fish- 
ponds of Great Mandailing (Penjabungan), Rao and Panti, and Padang 
Sidempuan and in Lake Manindjau (cf. SCHÜFFNER, SWELLENGREBEL, 
SWELLENGREBEL-DE GRAAF and MOCHTAR (°°) ). !) 
I will immediately add that, as SWELLENGREBEL (°8) also says, it is not 
yet an established fact that the inland-/zdlowi of Sumatra is identical with 
the common sea-coast /udlowi. In this connection I do not hesitate to 
concur with DAMMERMAN (%), who recently in a popular article expressed 
surprise at the fact that no one has thus far undertaken the experiment 
of starting from a given pair of Anophelines and raising their brood under 
various conditions. It might also be tried to construct frequency curves of 
some adequate countable characteristics for our common sea-coast /udlowi and 
for the inland-/zdlowi of Sumatra, and likewise for the sea-coast ludlowi 
artificially reared in the Sumatra fresh water fish-ponds and for the inland- 
ludlowi of Sumatra raised in the littoral brackish water breeding places. It 
would then appear to what extent the common coast-/udlowi and the inland- 
ludlowi of Sumatra are identical. 
I can not conclude this chapter without saying a few words about 
the measures which are required to make the tsatavia empangs innocuous 
as sources of the malaria peril. 
The draining dry of the marine fish-ponds along the coast of Batavia 
was resolved upon, mainly on the ground of the report made by Mr. VAN 
BREEMEN and myself (2) to the Commissioners of Public Health for the 
capital of Batavia (Gezondheidscommissie voor de hoofdplaats Batavia) on 
January the 3rd 1919, which report was published (with a great many 
misprints) in the City Gazette (Gemeenteblad) of Batavia No. 9, 1919 (°?). 
I) After this chapter had been written I visited in October and November 1921 
the ludlowi breeding places in the interior of Sumatra. Before long I hope to report at 
length in an other publication upon the data and the material collected during this 
journey. The conditions under which the aquatic stages of the Sumatra inland-ludlowi 
lived in the fresh water fish ponds of Penjabungan, Padang Sidempuan and Rao resembled 
in many respects those under which the larvae of the common sea-coast /udlowi thrive 
in the Batavia empangs, Thick floating masses of filamentous Schizophyceae occurring 
in the fresh water fish ponds of Sumatra recalled the Chaetomorpha masses of the 
Batavia empangs. The part played sometimes in the Batavia empangs, when the salinity 
of the pond water is not too high, by Najas falciculata R. BR. was played in the fresh 
water fish ponds of Sumatra by Hydrilla verticillata CASP. and to a lesser degree also 
by Najas sp. and Ceratophyllum sp. . 
In Lake Manindjau the occurrence of /udlowi larvae was also connected with the 
presence of floating masses of filamentous Schizophyceae and submerged masses of 
Hydrilla verticillata CASP. reaching up to the surface of the water. Outside the rushes 
of Lake Manindjau (cf. SCHÜFFNER, SWELLENGREBEL, SWELLENGREBEL—DE GRAAF and 
MOCHTAR(%)) (= Heleocharis plantaginoidea W.H. WIGHT) | found far more ludlowi 
larvae than between them. 
