CHAPTER V 



THE MUTATION THEORY 



When with the thoughts suggested in the last chapter we 

 contemplate the problem of Evolution at large the hope at the 

 present time of constructing even a mental picture of that process 

 grows weak almost to the point of vanishing. We are left 

 wondering that so lately men in general, whether scientific or 

 lay, were so easily satisfied. Our satisfaction, as we now see, 

 was chiefly founded on ignorance. 



Every specific evolutionary change must represent a definite 

 event in the construction of the living complex. That event 

 may be a disturbance in the meristic system, showing itself in 

 a change in the frequency of the repetitions or in the distribution 

 of differentiation among them, or again it may be a chemical 

 change, adding or removing some factor from the sum total. 



If an attempt be made to apply these conceptions to an actual 

 series of allied species the complexity of the problem is such that 

 the mind is appalled. Ideas which in the abstract are appre- 

 hended and accepted with facility fade away before the concrete 

 case. It is easy to imagine how Man was evolved from an 

 Amoeba, but we cannot form a plausible guess as to how Veronica 

 agrestis and Veronica polita were evolved, either one from the 

 other, or both from a common form. We have not even an 

 inkling of the steps by which a Silver Wyandotte fowl descended 

 from Callus Bankiva, and we can scarcely even believe that it 

 did. The Wyandotte has its enormous size, its rose comb, its 

 silver lacing, its tame spirit, and its high egg production. The 

 tameness and the high egg production are probably enough both 

 recessives, and though we cannot guess how the corresponding 

 dominant factors have got lost, it is not very difficult to imagine 

 that they were lost somehow. But the rose comb and the silver 

 colour are dominants. The heavy weight also appears in the 

 crosses with Leghorns, but we need not at once conclude that it 



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