STUDIKS ON HIGH AND LOW NON-DISJUNCTION 107 



of vermilion eye-color. Thus in 443 there were 53 not-verniilions and 

 39 vermilions and in 446 there were 96 not-vermilions and 37 ver- 

 milions. The most probable explanation is that vermilion had re- 

 mutated in the 6-pl stock since from crosses made later it was clear 

 that the new vermilion was inherited like the old one and since the 

 different crossover classes (as seen in table 18) were those which were 

 to be expected. The great excess of the not-vermilion class may be 

 explained from the fact that in the crosses from table 5 there were 

 taken more than one male. If the males really carried vermilion in 

 addition to ruby this should of course have been detected if they had 

 been examined but may also have been overlooked when taking them 

 from stock. 



Mutation from lethal to not-lethal. The mother of culture 636 

 (table 3) had the X-chromosome of the eosin line and carried thus in 

 one of them the lethals // and /;. She produced 47 daughters and 23 

 sons. One of her regular daughters was the mother of culture 674 

 (table 15). From a priori grounds it was equally possible that she 

 had inherited none of the lethals, one of them or both the lethals. 

 As she produced 114 regular daughters and only 58 regular sons it is 

 clear that she carried at least one of the lethals (No classification of 

 regular males was made and it is therefore impossible to say which 

 of the lethals it was that she carried). As a consequence one of her 

 exceptional daughters (culture 711, table 15) produced 71 regular 

 daughters and 39 regular sons and one of the exceptional daughters 

 from this culture again produced 106 regular daughters and 59 regular 

 males (738, table 15). In all these cases there occurred thus the 

 sex-ratio 2 Ç: 1 J" among the regular offspring, indicating that there 

 were some sex-linked lethals present. However, in the cultures 712 

 and 737 (table 15) where the mothers as in culture 711 were excep- 

 tional daughters from 674 (table 15) the regular offspring were 91 

 daughters 68 sons and 61 daughters 49 sons respectively or the sex- 

 ratios 1,3 Ç : 1 cT and 1,2 Ç: 1 J". From culture 712 it is furthermore 

 known that there really occurred at least one male which of the mutant 

 genes only showed eosin. (This male was kept for other purposes). 

 As now the loci for // and /, are 7,5 and 16,4 respectively it is highly im- 

 probable that an eosin male could have occurred if any one of these 

 lethals had been present in the mother of culture 712. From this 

 culture 712 there was furthermore taken an exceptional daughter (cul- 

 ture 746, table 15) and she produced 110 regular daughters and 84 

 regular sons (sex-ratio 1..3 Ç: 1 J'). Here again no classification of the 



