XXXI 

 THE FOUNTAIN OF CHANGE 



ONE of the fundamental problems of Biology 

 is the origin of the distinctively new. A 

 clever and well-proportioned dwarf is born in a 

 family, and the interesting type may reappear in 

 a certain proportion of his descendants for at least 

 four generations. The unsolved problem is : What 

 conditioned the dwarf? It is the same problem 

 as the origin of the mathematical or the musical 

 genius, the old problem of new departures. It is 

 difficult to draw the line, but it seems possible to 

 discriminate between minor novelties or " fluctua- 

 tions/' which differ but slightly from the parent 

 type or may be connected with it by intermediate 

 gradations, and the major novelties or " mutations " 

 which represent more or less of a new pattern and 

 are discontinuous. The contrast is not so much 

 in the amount as in the kind of change. The 

 copper beech, which made its appearance in the 

 seventeenth century, may not differ very materially 

 from an ordinary beech, but it was a discontinuous 

 variant which arose abruptly and came to stay. 

 Similarly, the white rat does not seem to want very 

 much to make it a brown rat the species whence it 

 sprang but it was in its day a new departure, and 



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