After Morgan 



MUTATIONS OF THE FRUIT-FLY 



In the course of systematic observation and experimenting, Morgan and his associates 

 found hundreds of individual fruitflies that arose as distinct types year after year. 

 They differed from their parents in a single character, sometimes in several characters 

 — eye color, wing shape, body color or shape, and many other details 



showed at least that without modifying the parent, something may happen 

 to the germ cells in a way that alters the characteristics of the offspring. It 

 did not enable us to produce particular mutations at will, nor did it tell us 

 exactly how the X rays exert their influence. Among these mutants, as among 

 those which appeared "naturally" in the laboratories of other investigators, 

 were some with white eyes, some with smaller wings, and many other freaks. 

 Many of these were entirely new in the sense that they had not been found 

 by other experimenters or observed to occur "naturally". 



In recent years startling results have been produced by treating plants 

 with the drug colchicine, obtained from a plant of the crocus family. The first 

 effect observed is a great increase in the size of parts treated, often associated 

 with coarse tissues or rank growth. The giant character is inherited. Closer 

 study indicates that the colchicine acts upon cells at the time the nucleus 

 divides, by keeping newly formed chromosomes from separating into two 

 sets. The result is a doubling of the chromosomes, and a modifying of the 

 growth and other characteristics. A "harvest spray" containing colchicine 

 has been used to keep apples of Mcintosh and other varieties from dropping 

 off the stem too soon while ripening. This spray improves the quality as 

 well as the yield, from the orchardist's point of view. 



We have every reason to think that new forms are constantly arising, more 



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