SELECTION: ORGANIC AND SOCIAL 195 



of fitness is familiar ; we are irresistibly pleased 

 in our own affairs with arrangements like safety- 

 valves and regulators which bring about important 

 results in an effective way ; we pour contempt on 

 tools that will not work, on machines that will not 

 go. But we have not to travel beyond our own 

 bodies to find illustrations of safety-valves and 

 regulators that put to scorn all machinery, and 

 one of the perennial delights of natural history, 

 in the wide sense, is its continual discovery of 

 fresh instances of hand-and-glove adaptations. 



There is wonderful fitness even in one of the 

 lowest forms of life it is always changing and yet 

 it remains the same, it answers back effectively 

 to external stimuli, it grows and passes from one 

 phase to another, it reproduces itself, arid it is 

 said that some of the simplest never die. We 

 cannot, at present, get behind this primary 

 adaptiveness of living creatures it is implied in 

 what we mean by living. It is convenient, however, 

 to keep the word " adaptation " for something 

 super-added to what we must take for granted, 

 and yet it is difficult to draw the line. The power 

 of growth is a primary attribute ; the capacity of 

 regrowing a readily broken limb depends on 

 this ; and yet it is difficult to understand why, 

 for instance, a chameleon should not be able to 

 regrow its tail, as almost all other lizards can do, 

 unless we regard the distribution of the regenerative 

 capacity as adaptive, adjusted in the course of 

 ages to frequently recurrent needs. We say that 

 the immunity which certain organisms have to 

 certain poisons is an adaptation, it has been 

 wrought out and added on ; but is it not, perhaps, 

 a special case of the immunity which even simple 



