2 
550 JACQUES LOEB AND HARDOLPH WASTENEYS 
A series of experiments was carried out in which fish were kept 
in a thermostat at 30°C. for various lengths of time to test whether 
this accelerated their adaptation to a temperature of 35°. This 
was true only to a slight extent. In all these experiments the fish 
were suddenly transferred to an m/4 Ringer solution at 35°. 
We were curious to know if these animals could also survive if 
suddenly transferred to a temperature of 35° in distilled water. 
This is indeed the case as table 7 shows. 
Fundulus can become adapted to a temperature of 35° in dis- 
tilled water if they are kept for two days or longer at a tempera- 
ture of 27°. It seemed to make no difference whether the fish 
had been kept at 27° in m/4 sea-water or in distilled water. 
TABLE 7 
| 
| DURATION OF LIFE OF FUNDULUS IF SUDDENLY 
C. 
PREVIOUSLY EXPOSE tis 
SED TO 27° FOR PUT INTO DISTILLED WATER OF 35° 
0 days (control) 4’ 
2 days indefinite 
3 days indefinite 
Finally experiments were made to see to how high a tempera- 
ture these fish could be adapted in a week. By keeping the fish 
at a temperature of 27° over night and raising them during the 
day to a gradually higher temperature we found that they could 
be kept at the end of the week at a temperature of 40°C., for two 
hours without apparent injury. At a temperature of 41° they 
soon suffered in their power to maintain their equilibrium. They 
were Immune to a temperature of 40° not only in an m/4 Ringer 
solution, but also in an m/64 solution. The lot which was in dis- 
tilled water died early during the experiment through an accident. 
It is probable that Fundulus once adapted to a certain tempera- 
ture can stand this temperature in any concentration of a Ringer 
solution below m/4. 
