SUNIER: Marine fish-ponds of Batavia. 283 
partly fails, such as in the ponds of Heemraad Oost where the salinity 
keeps relatively low throughout the year, the autumnal maximum of mosquito 
production becomes immediately evident also for ludlowi (cf. Table VIII, 
Heemraad Oost). Mostly however, at least in a dry year, the autumnal 
maximum for /udiowi will be quite suppressed and even replaced by a 
very low minimum in connection with the high salinities which arise 
just then. 
The phenomenon that the rossii production declines in the spring, 
together with the further fact that when, after a period of high salinities, 
low salinities occur again suddenly the /zdlowi production does not 
immediately increase very greatly, may be confidently put down to the 
West-monsoon showers, the spring rains and the circumstance that the 
submerged vegetation reaches full development only gradually in the course 
of the spring. 
Finally I have not been able to find an explanation for the fact that 
from May to August 1919 the rossii production kept diminishing slightly 
all the time. It is no wonder that a single point like that should remain 
unexplained; the number of factors influencing the magnitude of the rossii 
or the /zdlowi production is from the nature of the case very great and 
many of them are likely to escape our notice for ever. 
VAN BREEMEN (38) has demonstrated that what TERBURGH had been 
able to ascertain before for Sourabaya and Semarang, viz. that the kam- 
pongs on the North-coast of Java where a great deal of malaria occurs, 
mostly exhibit an increased mortality in the months of July, August and 
September; and that such mortality must be chiefly attributed to malaria, 
also holds good for Batavia. 
From the above and from what is known concerning the great 
importance of /udlowi as a transmitter of malaria, the conclusion is certainly 
warranted that the increased mortality from malaria in July, August and 
September on the North-coast of Java, at least where the Zudlowi 
breeding-places are marine fish-ponds, is undoubtedly intimately connected 
with the fact, apparent from Mr. VAN BREEMEN’s and my investigation, that 
the /udlowi production of the marine fish-ponds reaches its maximum 
about the middle of the year, after which, at least in a year when a 
sufficiently dry East monsoon develops, it diminishes again very considerably 
in the autumn (September, October, November) and is sometimes arrested 
altogether. 
Also SWELLENGREBEL (°°) connects the increased rate of mortality 
from malaria in July, August and September with the fact which he observed 
at Semarang in 1918, just as CITROEN has done at Sourabaya (when ?), 
that Judlowi occur very plentifully especially in the dry season’), to 
‘disappear again in October-December. 
1) “in the dry season”? “In the first part of the dry season” or “about the middle 
of the year” would probably be more correct here. 
