STUDIES ON IIKill AND LOW NON-DISJUNCTION 



97 



TAHLK 16. 



Offspring of a scute cosiii forked regular non-disjunelionul (Umghler 



from 039 table 9 and of her exceptiomd female descendents when 



nuded to various males. 



Percentage of exeptions 9,5i ± 0,9o. 



10 we had a typical low percentage of exceptions and this ensures that 

 the something in the chromosomes which makes this percentage higher 

 than usual must be present in both the homologous chromosomes (or 

 absent from both the chromosomes if it is the absence of something 

 which produces the high percentage). And as a consequence, if there 

 is a gene or a set of genes which produce the high percentage, these 

 genes have no effect in flies heterozygous for all of them. 



III. DISCUSSION AND CONCLUSIONS. 



From the data reported in the preceding chapter there are not 

 many conchisions which can be drawn with absolute certainty. But in 

 maintaining the denotation X for the X-chromosomes originating from 

 the eosin line of high non-disjunction, the following points have been 

 proved by the experiments: 



1. Non-disjunctional females, which are homozygous for the two 

 X:s give always the high percentage of exceptions no matter from 

 where the F-chromosome and the autosomes originate. 



2. Non-disjunctional females which are heterozygous with respect 



Hereditas IV. 1 



