236 TREUBIA VOL. II, 2—4. 
— 
Therapon jarbua and de cupanus as fishes devouring mosquito- 
larvae and -pupae. 
As far as I am aware it is only SEYMOUR SEWELL and CHAUDHURI (?°) 
who mention the occurrence of Haplochilus (panchax (HAM. BUCH), 
melastigma MC. CLELL. or lineolatus C. V.?) in brackish water, namely 
at Port Canning in Bengal. 
Now the kepala timah is indoubtedly in its origin a genuine fresh- 
water fish, which as a matter of fact is true of the whole family of the _ 
Cyprinodontidae. Still a number of Cyprinodontidae also occur in brackish 
water. Moreover the Cyprinodontid Lebias calaritanus is known to occur 
in the salinae of Capodistria, whilst a number of species of the American 
genus Fundulus are known to bear not only with impunity (like the stickle- 
backs, Gasterosteus spp.) the being transferred suddenly from fresh into 
salt water, but even to bear living in salinities that are higher than those 
of sea-water. How much the highest salinities that the said species of 
Gasterosteus and Fundulus will stand amount to, I have not found 
mentioned in the literature available here. 
For the Batavia empangs I collected a number of rather rough but 
sufficiently practical data concerning the quantitative occurrence of kepala 
timah at different salinities. In each observation the salinity was determined 
and the simultaneous quantitative occurrence of kepala timah noted down, 
expressed in one of the following six terms: none visible; very few; few; 
present (in normal numbers); many; very many. 
The data collected in this manner have been put together in the schedule 
of page 237, which has been derived from the observation-table (Table IV). 
It appears clearly enough from this schedule that within the limits of 
the salinities mentioned in it (6.3 °/,,—84.6 °/,,) the quantitative occurrence 
of the kepala timah in the empangs is independent of the salinity. 
At the laboratory I have also made a few simple experiments on the 
power of resistance of the kepala timah against important and especially 
sudden alterations of the salinity. I first transferred a fairly large number 
of kepala timah which had been caught for me in the empangs, into water 
from the Batavia drinking-water supply. The animals hardly reacted upon 
this and all of them continued alive. A couple of days after I put of 
these animals living in drinking-water: 
a. three specimens in coast-water collected at the sea-shore salinity 25.8 °/,, 
b. three specimens in a mixture of sea-water and distilled water: salinity 28.8 °/,, 
c. five specimens in sea water: salinity 33.4 °/5, 
Especially in the case mentioned sub c. the animals shortly after the 
transference were noticeably less mobile than under normal conditions. They 
then quietly floated about close to the surface of the water, hardly moving 
their fins. But a couple of hours afterwards they again behaved quite 
normally, feeling evidently completely at home again in their new milieu, 
