108 



(iERT BONNIKR 



ditfeient regular males was made, it is true, but it was noted that 

 there occurred a numl)er of eosin, scute eosin, eosin forked and eosin 

 vermilion garnet forked males which clearly shows that no one of the 



lelhals // and /,• was at this time present 

 in these cultures. Thus there must have 

 been a mutation from one of the lethals 

 // or /,• to not-lethal. If we, however, add 

 the number of regular offspring from 

 cultures 712, 737 and 746 (table 15) we 

 have 262 regular females and 201 regular 

 males i. e. the sex-ratio 1,3 Ç : 1 çf which 

 also may be written 76,9 ^^ : 100 $. But 

 since according to Warren (1918) there 

 ordinarily occur 95 cT • 100 Ç it is seen 

 that though no lethals can have been 

 present in cultures 712, 737 and 746 it 

 is very probable that the mutation from 

 lethal to not-lethal is not a real reverse 

 mutation to the normal allelomorph but 

 to another allelomorph which does not 

 kill the males which carry it, but which 

 lowers their viability. 



A meristic variant. The eosin male 

 from culture 712 just spoken of had 

 rather peculiar characteristics and the in- 

 terest of this individual was more of a 

 general biologic than of a mere genetic 

 kind (fig. 2). On one side he carried 

 namely a quite normal wing and a nor- 

 mal balancer. On the other side, however, 

 the wing was cut off just at the base, but the halther had grown out 

 to a wing of normal size, normal venation and with all characters ty- 

 pical for the wings of Drosophila mekmogaster. He died within the 

 first day and produced no offspring but is now kept in alcohol. 



A meristic variant. 



V. SUMMARY. 



1. This paper deals with different percentages of exceptions in 

 various lines of non-disjunction in Drosophila mclanogastcr. 



