SCALES, MIRRORS, LEATHERS 



coming upon one of the most intimate of all the actions 

 accomplished by living matter, what is called its 

 metabolism, for the elementary constitution of the 

 creature is as much concerned in its creation as in its 

 preservation. The assimilating behaviour is not, per- 

 haps, the same in both cases. We see something of 

 it and we measure its external signs; but we don't get 

 much further, except in guesses. 



" Moreover, your question, like every other question 

 which is concerned with living nature, must be sup- 

 plemented by a series of others. To be complete, it 

 must go back to the earliest beginnings, and not stop 

 short at this relation between a certain structural 

 condition and a capacity for growth. It is by no 

 means unimportant to observe the spontaneous, pre- 

 cocious appearance of this change in the scaly structure. 

 The organism produces it by itself apart from any 

 other influence. Environment has nothing to do with 

 it. Your carp themselves make it perfectly plain that 

 whatever variations there are arise directly from the 

 creature itself, that they are accidental mutations, 

 intrinsic in the first instance, then brought by it, for 

 purposes of its own existence, under the control of 

 the factors of the environment which allow it to live. 

 These factors either refuse them or accept them. 

 According to the particular case in question, life 

 becomes restricted or settles down to conformity to 

 circumstances. Actually, the adaptation is a com- 

 promise determined, after the event, by the automatic 

 play of the relations between the creature and its 

 environment." 



" But what compromise," said my friend, " do you 

 find in these scaleless carp? They seem to me to be 

 under a definite disadvantage, since they have no pro- 

 tection. It seems to me that they are very badly off, 

 whereas the carp, with scales are much better provided. 

 Yet the least favoured seem to be the most prosperous, 

 while those which are better equipped, those which 



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