266 



Experimental Transformation of Species 



Fig. jy. Linkage of Characters in Fruit Fly 



A male fruit fly having black body color and vestigial wings is 

 mated to a normal wild female, that is, one with gray body color 

 and long wings. The offspring are all of the wild type, the muta- 

 tion characters (black, vestigial) being recessive. If now one of the 

 hybrid males is mated to a black female with vestigial wings, we 

 should expect, according to the theory of independent assortment 

 of the various characters, that the following generation would show 

 a new recombination of wing characters and body color. We find 

 instead that there are only two kinds of flies, similar to the two 

 types of the grandparents. In other words, the characters that went 

 into the cross together come out together. From Morgan, The 

 Physical Basis of Heredity, published by J. B. Lippincott Company. 



