88 The Source of Variability 



cfi 



— ft -c? 



^===. I 



4 -a 



Fig, 35. Leaf, bract, calyx, and corolla of the "wild" type (ch) of Primula 

 sinensis and of nine mutants affecting leaf and inflorescence shapes. All are 

 shown on a wild type background except the calyx of nn, which is shown on 

 a ChCh background. (After Anderson and DeWinton.) 



exemplify exactly the type of difference found to be established as 

 specific, generic, or even family characters in many orders of 

 insects (Fig. 36). The ancestors of many wingless insects such as 

 fleas and lice were undoubtedly normally winged insects bearing 

 analogous if not homologous alleles for shorter wings. 



Similar observations are on record for chromosomal mutations. 

 In natural populations of Drosophila, chromosomal inversions are 

 abundant and of many kinds, and similar inversions have become 

 established as distinctive features of some species of Drosophila 

 (Patterson and Stone, 1952). In the plants many natural populations 

 show aneuploidy, and in some cases this is considered to be the 



