LINKAGE GROUPS 99 



Drawing (c) in figure 43, represents "bent," so 

 called from the shaj^e of the wings. This mutant is 

 likewise very variable, often indistinguishable from 

 the wild type, yet when well developed strikingly 

 different from any other mutant. 



The third mutant (d) is called shaven. The 

 bristles and hairs are extremely short, and the thorax 

 esj^ecially, appears as though shaven. 



This brief account of a few of the mutant races 

 that can be most easily represented by uncolored 

 figiu'es will serve to show how all parts of the body 

 may change, some of the changes being so slight that 

 they would be overlooked except by an ex^^eii:, others 

 so great that the characters affected depart far from 

 the original one. 



It is important to note that the m utant genes in the 

 X -chromosomes are not limited to anij part of the 

 body, nor do theg affect more frequently a particu- 

 lar part. The same statement holds equally for all 

 of the other chromosomes. In fact, since each factor 

 may affect visibly several parts of the body at the 

 same time there are no grounds for expecting any 

 specicd relation between a given chromosome and 

 special regions of the body. It cannot too insistently 

 be urged that when tee say a character is the product 

 of a particular factor uce mean no more than that it is 

 the most conspicuous effect of that factor. 



If, then, as these and other results to be described 



