436 



G. W. DKLUZ HAMLETT. 



only flies heterozygous for the transposed piece. The comparison 

 of the homozygous and the heterozygous conditions with each 

 other is of especial interest because of its bearing on the problem 

 of the mode of attachment of the second chromosome fragment, 

 as will be shown later. 



The third chromosome mutant genes used in the experiments 

 are, in their order from left to right along the chromosome: 

 roughoid (ru), hairy (h), scarlet (st), pink (p), spineless (ss), 

 delta (A), hairless (H), ebony (e), rough (ro), and claret (ca). 

 Their locations are shown in the map of Fig. i. Translocation 

 is represented by Tr, and the deficient second chromosome by PI. 

 Curly (Cy) is a second chromosome gene used in balancing stocks. 

 The linkage in flies homozygous for Tr was tested in two experi- 

 ments. The summarized results for these crosses are given 

 below, in Tables I. and II. 



TABLE I. 



A H e Tr 



PI ru h st p ss 



Tr 



9 X ru h st p ss e cf 1 . 



TABLE II. 



Cy A H e Tr 



PI 



Tr ro ca 



9 X e ro ca cf 



Regional Crossover Frequencies. 



These figures show a remarkable drop below normal in t he- 

 crossover values as the locus of translocation is approached. 

 This may be seen by comparing their map values (see Fig. i, 



