148 



MORGAN— THE CONSTITUTION OF 



[April 23, 



The four pairs of chromosomes of Drosophila are shown in the 

 next diagram, Fig. 3. 



9 



d 



■^.^^.^ 



A. 



/v 



Fig. 3. Diagram of the four pairs of chromosomes of Drosophila ampel- 

 ophila; to the left the chromosomes of the female; to the right those of 

 the male. 



The correspondence between the four character groups and the 

 four pairs of chromosomes is obvious even to the size relations. 

 This relation, or correspondence, does not however tell us any- 

 thing in respect to the way in which the chromosomes stand for the 

 characters of the group. So far, the result only shows that the char- 

 acters of a given group are in some way represented in a particular 

 chromosome. Our work has, however, carried us beyond this point. 

 I may illustrate this by an example from the first group, containing 

 sex linked characters. We mean by sex linked characters that they 

 follow the known distribution of the X chromosomes. For in- 



