84 THEORY OF EVOLUTION 



the silkworm moth there have been described 

 four types of larvae, distinguished by different 

 color markings, that form a system of quad- 

 ruj^le allelomorphs. In Drosophila there is a 

 quintuple system of factors in the sex chromo- 

 some re2)resented by eye colors, a triple system 

 of body colors, and a triple system of factors for 

 eye colors in the third chromosome. 



Mutation and Evolution 



What bearing has the appearance of these 

 new types of Drosophila on the theory of evo- 

 lution may be asked. The objection has been 

 raised in fact that in the breeding work with 

 Drosophila we are dealing with artificial and 

 unnatural conditions. It has been more than 

 implied that results obtained from the breed- 

 ing pen, the seed pan, the flower pot and the 

 milk ])ottle do not apply to evolution in the 

 "open", nature "at large" or to "wild" types. 

 To be consistent, this same objection should be 

 extended to the use of the spectroscope in the 

 study of the evolution of the stars, to the use 

 of the test tube and the balance by the chemist, 

 of the galvanometer by the physicist. All these 



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