288 TREUBIA VOL. II, 2—4. 
Even without having witnessed with one’s own eyes how the malaria 
plague impresses its stamp of suffering on the whole existence of the 
population of the northern quarters of Batavia, it is possible, from the figures 
concerning spleen-index and mortality published by VAN BREEMEN (#8) (59), 
to gain an impression of the great loss and waste not only of human 
happiness and human life but also of energy and productive capacity 
which this population is doomed to suffer under the leaden weight of 
the endemic malaria fed and nurtured by the empangs. 
To such a state of things a final end can of course be put only by 
taking once for all radical and drastic measures, definitely rooting out the 
evil, such as the sanitation of the whole brackish water zone of Batavia 
which would include the draining of the empangs. 
It has been supposed that the requirements of sanitation could be 
satisfied by the constantly kept up removal of the submerged vegetation, 
which as we saw in Chapter IV spontaneously develops in the ponds 
and is composed of floating masses of Chaetomorpha forming conglomerates 
with the other plants mentioned in Chapter IV, which float at or reach 
up to just beneath the surface of the water, and by regularly keeping 
the margins of the ponds clear of overhanging land plants projecting 
partly into the water and cutting them straight down. The bandeng now 
feeding in the Batavia empangs on the submerged vegetation just specified, 
would then have to be reared on “tay-ayer” only (cf. Chapter IV). 
Apart from the question whether the Batavia bandeng rearers could 
really be successfully induced to feed the bandeng exclusively on, for 
example “tay-ayer” '), and no longer on the submerged vegetation 
floating at or reaching up to just beneath the surface of the water I highly 
doubt whether it would be practically possible to clear away all the time, 
in the whole Batavia pond district, 8.8 K.M. long and 0.8 to 1.8 K.M. 
wide, all the spontaneously and continually developing submerged vegetation 
before it begins to float or reaches the water surface by growing upward, 
and to keep all the pond margins clean. Moreover the question arises 
whether the empang-industry could bear the expenses of this continuous 
clearing away of the submerged vegetation and keeping clean of the edges 
of the ponds together with the cost of an effective supervision of this 
work. For surely these expenses should not be borne by the whole 
community but by the empang-industry itself. 
But there is still more. By clearing away the algal vegetation it would 
be highly probable that Haplochilus panchax (HAM. BUCH.) would be 
deprived of the opportunity of reproducing itself in the ponds. For, 
as | said in Chapter VI, in the empangs I found the eggs of this little 
fish exclusively between the Chaetomorpha filaments to which they are 
1)) Besides with “tay-ayer” the bandeng could at all events be fed also with 
Vaucheria, which alga resembles Chaetomorpha certainly more than “tay-ayer” as a 
bandeng food, and of which, as related in Chapter IV, I have always seen the masses 
keep near the bottom and never rise to the surface of ‘the water. 
