STUDIES ON HIGH AM) LOW NON-DISJUNCTION 



105 



it would be impossibic by a cylolo}:jical examination to detect such a 

 loss. If, however, the genes constitute a kind ol skeh'ton within the 

 genebasis then a cytological examination of the deficiency woidd result 

 in that the chromosome siiould be narrower in the deficient region but 

 that the chromosome would not be shortened (Fig. 1 B). Tliat is, 

 however, just what Mohr has found in a very carefully made cytological 

 examination of the Notch« — deficiency case. (His paper is now in 

 press). 



I wish once again to point out that although there are a very 

 great number of facts which point in such a direction as to prove the 

 correctness of the assumption that it is the length of the X which 

 determines the percentage of exceptions, this assumption must be 

 looked at as an alternative one until data to a greater extent are 

 available. I have therefore started a new set of experiments in which 

 the crosses are made in such a way as to avoid so many sources of 

 errors as possible and where special regard will be paid to the alter- 

 native explanation of the data that there is a complicated inter- 

 action betw^een many different genes for the percentage of exceptions. 



IV. MUTATIONS AND ABERRATIONS. 



As was to be expected there have during the experiment occurred 

 several mutations but most of them have until yet not been located. 

 Some lethals have been described in other papers (^Bonnier 1922 and 



TABLE 17. 



A wild type daughter from 671 table 16 was mated to a Bar male and 



produced a yellow daughter. This yellow female was mated to a wild 



male from stock and her offspring was: 



1923) and the list here below contains only mutations and aberrations 

 of a greater interest. 



Equationcd non-disjunction. From culture 671 (table 16) 6 wild 

 type regular daughters were taken and mated to Bar males from stock. 

 Of these six crosses, five were without anv interest. In one, however. 



