312 Proceedings of Indiana Academy of Science. 
females produce non-crossover gametes (b pv) and (BP V) and crossover 
gametes of the composition b P V—Bpy—bpV—BPy—bPv and Bpy. The 
males to which they are mated produce gametes of the composition b p y. 
The different classes realized are given in table XX. 
Table XX. Classes realized on back crossing the bpv <o& to the 
hybrid @ of composition bpv BPV. 
No. Vestigial Long 
Black Gray Black iray 
Purple | Red Purple | Red Purple | Red’ /|Purple | Red 
bpv bPv Ppv BPy bpV bPV | BpV BPV 
1 95 2 15 23 16 13 1 119 
2 62 4 6 5 8 14 2 78 
3 ila 4 14 9 15 16 2 89 
4 179 2 12 26 62 36 4 301 
Totals.| 447 12 47 63 101 79 9 587 
VI. Summary. 
The independent origin of curved, a wing mutant identical with 
the one reported by Bridges, is here given. The data obtained 
with the various crosses is in agreement with the great mass of evi- 
dence which shows that the chromosome conception of inheritance offers 
the only rational basis upon which such data can be interpreted. Genes 
carried by different chromosomes give free assortment with Mendelian 
ratios, those in the same chromosome show linkage with no crossing over 
in the male. 
It is evident that the factor grouping of a new mutant can be determined 
by the failure of the double recessive to appear in the F, generation. Mor- 
gan has made use of black-pink flies for testing a new mutant type. Black 
is in the second group and pink in the third. If the new factor belongs to 
either of these groups it will fail to show the double recessive among the 
grandchildren from the cross. The sex relations from such an experiment 
will readily determine whether or not it belongs to the sex-linked group. 
If it belongs to none of these groups it is by exclusion placed in the fourth 
group. 
