Affective Tendencies 371 
namely the artificial maintenance of the greatest possi- 
ble constancy in the environment, which is the necessary 
and sufficient condition for preserving physiological 
invariability. 
Il. 
Closely connected with this inherent fundamental 
tendency of every organism to strive to preserve its nor- 
mal physiological condition or to restore it as soon as it 
is disturbed, is still another attribute which in its turn 
becomes the source of new affectivities. 
For as soon as the previous stationary condition can- 
not be restored by any means, that is by any movements 
or change of location, the organism disposes itself in a 
new stationary condition consistent with its new external 
and internal environment. In this way there originate 
a large number of new phenomena called “adaptations.” 
Thus, for instance, Dallinger’s classical experiments 
on the acclimatization of lower organisms—suggested by 
the observation that many organisms usually living in 
water of an ordinary temperature, ‘also live and flourish 
in the hottest spring,—have proved that Infusoria may 
gradually become accustomed to a constantly higher tem- 
perature so that finally after years of continuous slow 
increase in the degree of heat, they can stand a tempera- 
ture so high that any other individual not acclimated 
would certainly die if subjected to it. It is likewise 
known that the same species of Protozoa are found in 
both fresh and salt water, and that it is possible to ac- 
custom fresh-water Amcebe and Infusoria to a salt 
habitat which would have killed them at the start,— 
and there are more instances of the same kind.’° 
10See C. B.. Davenport and W. E. Castle, “On the Acclimatisa- 
