SUNIER: Marine fish-ponds of Batavia. 269 
specialization if the kepala timah, living amidst all the small aquatic animals 
occurring in the empangs, should gobble up none of them except only 
the mosquito larvae and pupae. 
Furthermore in my examination of over 100 intestine-contents of as 
many kepala timah I invariably found in them Anopheline larvae and pupae 
or remains of these. The case where SWELLENGREBEL (%) did not find 
remains of Anopheline larvae in more than 2 out of 26 kepala timah 
therefore certainly does not represent the normal proportions, at least for 
the Batavia empangs. 
Consequently whereas the result of SWELLENGREBEL’s (°°) experiment 
with Aaplochilus panchax (HAM. BUCH.) fits entirely with my amply 
expounded views of the importance of this little fish as an eradicator of 
mosquito larvae and pupae, SWELLENGREBEL’s (°”) observations just mentioned 
do not induce me to modify these views. 
From a few experiments made with Ophiocephalus striatus BL. and 
Dangila cuvieri C. V. kept in 3 L. glasses or in 10 L. tins SWELLENGREBEL (°”) 
further supposes the conclusion warranted that a mechanical protection of 
the Anopheline larvae and pupae by floating and submerged water plants 
does not exist. According to him the swarming presence of those larvae 
and pupae in the very places where there are also floating and submerged 
water plants is due exclusively to the circumstances that 1° among those 
plants there always live numerous other small animals also preyed upon 
by the fish and which therefore partly divert the attention of the latter from 
the mosquito larvae and pupae, and 2° that the water-plants supply the 
food of the mosquito larvae. 
I can agree with the statement sub 1°; as to the remark sub 2° I have 
already said above that I am quite willing to agree that, apart from the 
mechanical protection offered to the mosquito larvae and pupae by the 
floating algal masses and by the submerged vegetation reaching up to 
just beneath the surface of the water, the conditions of life for the Anophe- 
line larvae and pupae may perhaps be more favourable in yet many 
other respects, a. o. as regards food, amid the submerged vegetation than 
in open pond water. Yet it is apparent that too much importance should 
not be attached to this in view of the enormous production of mosquitos 
observed by Mr. VAN BREEMEN and myself in the ponds of Heemraad 
Oost where the submerged or floating masses of water plants were entirely 
missing, nay in which to the naked eye not a single alga-thread nor a 
blade or leaf was to be perceived. 
Furthermore I would not like to conclude, as SWELLENDGREBEL (€?) does 
from the few experiments taken with Ophiocephalus striatus BL. and 
Dangila cuviert C. V. under circumstances widely different from the natural 
conditions of life of those animals, that “the protection afforded by the 
plants” (scil. floating and submerged water plants) ‘is not a mechanical one.” 
It seems to me superfluous to go any further into this matter now. 
