ADAPTATION OF FISH TO TEMPERATURE Nu) 
into a m/4 Ringer solution of a temperature of 35° (A). Simul- 
taneously fish which had been immunized for 35° by keeping them 
three days at 27° and which had then been kept at between 10° . 
and 14° for nineteen days were also put into a m/4 Ringer solution 
of 35° (B). In addition two controls were made: Fish kept on 
ice at 0°.4 for twenty days but not previously immunized (C), 
and fish not previously immunized kept for several weeks at a 
temperature of from 10° to 14° (D) were also suddenly transferred | 
to a temperature of 35°. Table 10 gives the result. 
TABLE 10 
DURATION OF LIFE OF FISH AT 35°C. IN m/4 RINGER SOLUTION 
— 
Gi immunizedibutkent B. Immunized but C. Not immunized 
Bein D. Not immunized 
kept at 10° for nine- kept on ice for z 
on ice for fourteen days teen n days twenty days kept in cold room 
Alive after3 hours. One alive after 3 Die in 2’ | Die in 2’ 
hours | 
The experiment was repeated with the same result, only those 
in lot A and B remained all alive. It is therefore obvious that 
the resistance acquired for a higher temperature (35°) is not lost 
or diminished if the fish are kept for two weeks on ice. 
THEORETICAL 
The phenomenon of adaptation considered in this paper is the 
fact that fish can resist a high temperature better if the latter 
is raised gradually than when it is raised suddenly. Physies offers 
us an analogy to this phenomenon in the experience that glass 
vessels which burst easily when their temperature is raised sud- 
denly, remain intact when the temperature is raised gradually. 
This phenomenon finds its explanation in the fact that glass is 
a poor conductor of heat and that when the temperature is raised 
suddenly, e.g., inside a glass cylinder, the inner layer of the cylinder 
expands while the outer layer, on account of the slowness of the 
conduction of heat, does not expand equally and the cylinder 
bursts. 
