SUNIER: Marine fish-ponds of Batavia. 289 
fastened by a special differentiation of the egg-membranes. These eggs 
of Haplochilus panchax, which do not float but sink, will certainly not 
be able to develop on the mud bottom of a pond deprived of vegetation. 
And we have seen before how great may be the production of 
Anophelines of open empang-water without any vegetation, when Haplo- 
chilus panchax is absent from it! The complete. clearing away of the 
submerged vegetation might accordingly lead to a result the exact opposite 
of the one intended. 
It would however appear to me that the chance of the attempt ever 
being made to make harmless so extensive and dangerous a breeding place 
of malaria mosquitos close to a large town as the Batavia empang zone 
by the constant clearing away of the submerged vegetation floating at or 
reaching up to just beneath the water-surface and by keeping the pond 
margins clean, is very slight indeed. 
In the second place the question has often been asked whether, upon 
the disappearance of the marine fish-ponds near Batavia, the /zdlowi would 
not remove to other breeding places where they did not occur as long as 
the empangs were in existence. That this question would not be devoid 
of interest one might gather from the following words of SWELLENGREBEL (°°): 
“When there are no fish-ponds in a littoral district the /zdlowi larvae 
“are found in breeding places, in which they are not found wherever 
“fish-ponds do exist. We will indicate this phenomenon by the name of 
“deviation of breeding places”. j 
“When there are no fish-ponds in a littoral zone and they (or at least 
“sheets of water that are similar to them in their vegetation) are afterwards 
“formed, then the /zdlowi disappears from the breeding places where they 
“formerly did occur, and concentrate on the new, more favourable ones: 
“a still clearer instance of the deviation of breeding places”. 
Now DAMMERMAN (°) has recently pointed out that for this so-called 
deviation of the breeding places of mosquitos sufficient proofs have never 
been given. Neither has it become clear to me on the strength of what 
data SWELLENGREBEL (°%) thinks the conclusion warranted that in a littoral 
zone without fish-ponds /zdlowi larvae are found in certain breeding places, 
where they would not be found in parts where fish-ponds do exist. He 
nowhere supplies systematic data on the strength of which such a far-reaching 
conclusion could be drawn with any certainty. On the contrary, from what 
he has said before, and likewise from VAN BREEMEN’s investigations (*?) (°°), 
it is apparent that in a coastal region with salt water fish-ponds /zdlowi 
larvae may still be met with outside the fish-ponds in other breeding places, 
albeit not in such great quantities as in the ponds themselves. 
Furthermore it does not seem an easy thing to observe and ascertain 
with sufficient accuracy what SWELLENGREBEL (55) mentions in the second 
place, to wit, the total disappearance of /udlowi from an old, less favourably 
situated breeding-place, and the simultaneous appearance of Zudlowi in more 
