556 
ZOOLOGY: A. H. STURTEVANT 
similar results; but those descendants known not to have received it 
gave the 'usual' result. This was true whether the chromosome 
came from the mother (as above) or from the father. And when other 
second chromosome genes were substituted for vestigial and speck, un- 
usual ratios still appeared; but for any combination the result was 
relatively constant, and the combined 'unusual' results give as con- 
sistent a scheme as the 'usual' results. The first column of table 1 
shows the percentage of crossing over in the ordinary females for various 
combinations of second chromosome genes. ^ The second column gives 
similar data for tests of females that carry a Nova Scotia chromosome. 
Figures 1 and 2 are chromosome maps constructed on the basis of these 
two columns. 
Fiq.l 
Si 
00 02 13 IH 
Fiq.3 
S' prvgc sp 
H 1 —Ht- 
H2 ^- '/y.f "BOA 
t Pr 
S' Ir pr 
A large number of these experiments have been made with females 
having one Nova Scotia chromosome, and its mate bearing the mutant 
genes black, purple, and curved. Numerous tests have been made in 
order to determine the nature of the crossovers produced. It has been 
found that those crossovers that receive the part of the original Nova 
Scotia chromosome lying to the left of the purple locus still give unusual 
results and transmit the peculiarity to all of their descendants that 
receive this piece. The results produced by such females are not, how- 
ever, the same as those produced when all the Nova Scotia chromosome 
