ON THE ADAPTATION OF FISH (FUNDULUS) TO 
HIGHER TEMPERATURES 
JACQUES LOEB anp HARDOLPH WASTENEYS 
From the Rockefeller Institute, New York 
I. INTRODUCTION 
It is a well known fact that organisms can stand a higher tem- 
perature if the latter is raised gradually than if it is raised sud- 
denly. This phenomenon is referred to‘in biology as a case of 
adaptation. Dallinger states that he succeeded in adapting cer- 
tain protozoa to a temperature of 70° by gradually raising their 
temperature during several years. 
Schottelius had found that colonies of Micrococcus prodigi- 
osus when transferred from a temperature of 22° to that of 38° 
no longer formed pigment and trimethylamin. When transferred 
back to the temperature of 18° to 22° the formation of pigment 
and of trimethylamin was resumed. After the cocci had been 
cultivated for ten or fifteen generations at 38° they failed to form 
pigment even when transferred back to 22°. 
These experiments became the starting point for similar experi- 
ments by Dieudonné. He used Bacillus fluorescens putidus which 
forms a fluorescein pigment and trimethylamin. The optimal 
temperature for this bacillus is 22°. At 35° it grew but did not 
form pigment or trimethylamin. At 37°.5 growth ceased. Re- 
transferred to 22° pigment and trimethylamin were again formed. 
Dieudonné! exposed a culture of this bacillus to 35°. After 
twenty-four hours a second culture was taken from this and also 
kept at 35°, and this process was repeated each day. The fif- 
teenth generation thus cultivated at 35° began to form some pig- 
ment and from the eighteenth generation on, at 35° the formation 
! Dieudonné, Arb. aus dem kaiserl. Gesundheitsamte, vol. 9, p. 492, 1894. 
543 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 12, No. 4 
