SUNIER: Marine fish-ponds of Batavia. 255 
collect a water-sample and frequently also a sample of the submerged 
vegetation. The composition of the samples of the submerged vegetation 
was examined by me and | also determined the salinity of the water-samples. 
In this manner Mr. VAN BREEMEN and I collected 490 sets of combined 
data, laid down in the observation-table (Table IV). The salinity of the 
water was determined in 489 cases, one water-sample being lost before it 
had been examined. Analyses of samples of the submerged vegetation 
gathered in the observation-places were made in 226 cases. 
As regards the figures given for the Anophelines, when in March 1918 
Mr. VAN BREEMEN and | started the regular collection of data at the 
Batavia empangs, Anopheline-larvae and -pupae were being caught in the 
marine fish ponds by the Public Health Service, in the manner indicated 
by SCHÜFFNER and SWELLENGREBEL (°!) (page 55), i.e. by means of white 
enamelled plates, white enamelled rice spoons and empty quinine bottles. 
As it is impossible to distinguish from each other the larvae of the two 
species of Anophelines produced by the Batavia empangs, viz. of the dan- 
gerous malaria transmitter Myzomyia ludlowi THEOBALD and of Myzomyia 
rossit GILES, salt-water type (cf. a.o. MANGKUWINOTO (*) and SWELLEN- 
GREBEL (°7) (°8)), the only thing to do then was to determine the imagines 
which afterwards developed from the larvae and pupae collected '). 
From the beginning it seemed to me that it would be very difficult 
to obtain by this method adequate, and by adequate should be understood 
here comparable quantitative data concerning the production of different 
species of Anophelines by various breeding-places. I therefore proposed 
to Mr. VAN BREEMEN to proceed to catches by mosquito-nets, which 
would yield data relative to the production of Anophelines per unit of sur- 
face-area of the breeding-place and per night. | subsequently learned that 
also Sir RONALD ROSS (3) as early as 1908 had made use of mosquito-nets, 
in order to study the production of Anophelines of “Clairfond Marsh”, 
Mauritius. 
Ross discusses these catches with mosquito-nets in his well-known 
work “The prevention of malaria” (2) (cf. pages 165 and 166 and the 
upper illustration facing page 166). On that occasion he points out how 
great is the need of adequate quantitative data of this nature, collected by 
means of mosquito-nets. 
Mr. VAN BREEMEN accordingly had mosquito-nets. made of a model 
of his own devising. These mosquito-nets are to be seen in our photos 
14 and 15 (Plates XXII and XXIII). At the bottom they are held open 
by a square frame composed of four bamboos, which floats and encloses 
exactly 1 M? of the water surface. At the top the mosquito-gauze is 
I) Pupae of Anophelines are not described either by MANGKUWINOTO (5), or by 
SWELLENGREBEL (4°) (57) (58), or by SCHÜFFNER and VAN DER HEYDEN (°). In this con- 
nection the question arises as to whether the pupae of Myzomyia ludlowi THEOBALD 
and Myzomyia rossii GILES, salt-water type of MANGKUWINOTO (%) are distinguishable 
from each other. 
