238 | TREUBIA VOL. Il, 2—4. 
and they eagerly ate the mosquito-larvae and -pupae with which they 
were fed. 
Of the animals mentioned sub c., living in seawater of 33.40/,,, I trans- 
ferred two, a couple of days later, into distilled water prepared in my 
laboratory. Also in this case the animals were far less mobile than in 
normal circumstances, though only for a short time after the transference. 
But instead of floating at the surface, this time they rested with their bellies 
on the glass bottom ot the aquarium filled with distilled water, into which 
they had been put. Yet the animals soon behaved quite normally again. 
A couple of days after, I transferred these same kepala timah back again 
from the distilled water to the seawater of 33.4 °/o. This also they bore 
well, all five of them. 
Next I again conveyed 10 kepala timah from fish-pond water of 27. 8 °/00 
salinity into distilled water, in which again the animals soon appeared to 
be feeling at home. 
Hereupon I] made some experiments on the transference of kepala 
timah from distilled water into water of a higher salinity than that of sea- 
water. For this purpose I drew about two pints of pond-water of a high 
salinity by means of a waterjet suction-pump through some filter-candles- 
The pond-water thus purified proved to have a salinity of 62.9 °/o) (deter- 
mined by means of a KiiCHLER areometer and a thermometer after diluting 
one weight-part of this water with one weight-part of distilled water). 
By mixing this water with smaller or larger quantities of distilled water, 
solutions of different concentrations were obtained. 
The fish then transferred were: 
a. 2 kepala timah from distilled water into water of a salinity of 62.9 °/¢ 
b. 3 ” „ ” „ ” ” ” ” » 1» 52.4 0/00 
C 3 ” ” „ ” ” „ ” ” ” ” 41 9 0/00. 
All these animals died within a few hours. Only one of those mentioned 
sub 5 did not die till a little more than 24 hours later. 
From the above it therefore results that in my laboratory kepala timah 
drawn from the Batavia empangs, after living a couple of days in distilled 
water: 
did bear being suddenly transferred from distilled water to water 
of a salinity of 33.4 °/o or less, together with being inversely conveyed 
back again suddenly into distilled water; 
did not bear being suddenly transferred from distilled water into 
water whose salinity amounted to 41.9 °/o) or more. . 
Afterwards I also put a number of kepala timah from pond-water 
wherein they were living naturally when caught and whose salinity 
amounted to 27.8 °/ into solutions of different salinities. The result of 
this is synoptically tabulated as follows: 
