194 EVOLUTION 



and leaf-closure. The cold of winter is 

 probably the stimulus rather than the efficient 

 cause of the brown stoat becoming the white 

 ermine. 



(3) To some of the irregular changes in its 

 surroundings the living creature is able to 

 adjust itself temporarily. The warm-blooded 

 bird or mammal can within limits adjust its 

 heat-production and heat-loss so that the 

 temperature of the body remains the same 

 whether that of the environment rises or falls. 

 In the case of many of these transient adjust- 

 ments there remains no abiding result that 

 can be detected. 



(4) Insensibly, however for it is all a matter 

 of degree we pass to cases where the re- 

 sponses to environmental change last for a 

 considerable time. Sun-burning on a summer 

 holiday, increase hi the size of a muscle after 

 a course of exercises, the blanching of the 

 banked-up celery are familiar illustrations. 

 The bodily change has taken a firmer hold 

 than in the case of transient adjustments, but 

 it is still a passing change. Like a bow 

 unstrung the organism rebounds, approxi- 

 mately to its previous state. 



Semon has recently propounded a theory 

 of the " Mneme " which is of interest in 

 this connection. The general idea of it is, 



