SEX-LINKED INHERITANCE IN DROSOPHILA 89 



therefore, does not follow X in its distribution. Its absence is 

 indicated by small y. In all there were five crosses with their 

 reciprocals^ or a total of ten combinations. 



/ SRB 9 by LWY d' 



\ SRB c^ by LWY 9 



/ LWB 9 by SRY c^ 



\ LWB cT by SRY 9 



/ SWB 9 by LRY cf 



\ SWB d^ by LRY 9 



/ LRB 9 by SWY d' 



\ LRB d by SWY 9 



/ SRB 9 by LWN d 



\ SRB d by LWN 9 



Three combinations, viz: the second, third and fourth gave 

 some anomalous results and have been withdrawn in order that 

 they may be repeated. 



In representing the gametes of Fi we have followed the plan of 

 writing in the upper line of 'Eggs,' in the two middle terms, the 

 two combinations that come direct from the paternal and maternal 

 gametes, and at their sides, right and left, the eggs that come 

 from the free distribution of Y and y. In the second line of eggs, 

 written in similar sequence, are the crossing-over of long and short. 

 The crossing of RB and Wb (or similar combinations) is not given, 

 but can be readily conceived. It is the latter that gives the 

 small classes of crossing-over for color (eye and body color) which 

 follow the numerical data of the larger classes. The sperms are 

 given in the third line of gametes and since by the hypothesis here 

 followed no crossing-over in the gametes of the males is allowable, 

 only one line (of four classes) is represented. In the sperm the 

 yellow factor freely interchanges, since it shows no linkage with 

 the sex-factor X. The results fully justify this assumption. In- 

 stead of writing out all the combinations of egg and sperm, a 

 summary only of the expected results is given at the end of the 

 analyses. 



