OF MUTANT CHARACTERS. 



235 



morula, and 160 were double cross-overs (table 84). The total cross- 

 overs between arc and morula were 534 or 7.9 per cent. The black 

 arc cross-over value was 43.4 per cent and the black morula 4(3. G per 

 cent, which agrees with the 46.8 per cent found in the former black 

 morula back-cross. These values and the smallness of certain cla.ssos 

 thereby known to be double cross-over classes established the position 

 of morula to the right of arc, and 7.9 units distant. 



Table 84. — The four complemetitary hack-cross experiments giving data on the 



relations of black arc, atid morula. 



The coincidence of 69.1 per cent 



/160X6794X100 



')■ 



= 69.1) is rather 



2951X534 



low for distances so long and indicates that a cross-over between arc 

 and- morula is only 69 per cent as likely to be accompanied by a cross- 

 over between black and arc, as would be the case if the two regions 

 were independent. 



Table 85. — Summary of the cross-over data involving morula. 



The purple arc speck back-cross (table 54) had given 5.9 units to 

 the right of speck. Morula is therefore situated about 2 units to the 

 right of speck. A summary of all the cross-over data including m(iriila 

 is given in table 85, from which the locus of morula is calculated as 

 106.3 on the basis of star as the zero-point. 



