Coincidence. 



75 



XII. COINCIDENCE. 



Coincidence in the X chromosome of D. virilis appears to resemble 

 that in D. melanogaster, as has already been noted by Weinstein 

 (1920). Since this subject is being investigated in detail by Dr. 

 Weinstein, we will confine ourselves to a tabulation of the values 

 obtained from the new data in the present paper. In most cases the 

 numbers are not large enough to be satisfactory, but the results 

 agree with previous ones in indicating a resemblance to those obtained 

 from D. melanogaster. 



In table 8 the data are given in order, according to the map region 

 involved, beginning with the uppermost loci. The cases involving 

 more than 25 double cross-overs and more than 900 flies are sum- 

 marized separately in table 9, and are arranged in accordance with 

 map-distance rather than map-region. In both tables the column 

 headed "Calculated distance" gives the "distance" between the 

 uppermost and lowermost loci, calculated from the particular 

 experiments involved. Under "Map-distance" is given the cor- 

 responding value taken from the final map (fig. 7). The latter is 

 the larger value in most cases. 



