NEW DATA. 



LINKAGE OF CHERRY AND SABLE. 



37 



The origin of cherry eye-color (Plate II, fig. 9) has been given by 

 Safir (Biol. Bull., 191 3). From considerations which will be dis- 

 cussed later in this paper we regard cherry as allelomorphic to white in 

 a quadruple allelomorph system composed of white, eosin, cherry, and 

 their normal red allelomorph. Cherry will then occupy the same locus 

 as white, which is one unit to the right of yellow, and will show the 

 same linkage relations to other factors as does white. A slightly lower 

 cross-over value should be given by cherry and sable than was given 

 by yellow and sable. 



When cherry (gray) females were crossed to (red) sable males the 

 daughters were wild type and the sons cherry. Inbred these gave the 

 results shown in table 10, 



Table 10. — Pi cherry 9 9 X sahle cf cf. Fi wild-type 9 X Pi cherry d'cf . 



The percentage of crossing-over between cherry and sable is 42. 

 Since cherry is one point from yellowy this result agrees extremely well 

 with the value 43 for yellow and sable. Since yellow and eosin lie at 

 the left end of the first chromosome, the high values, namely, 43 and 42, 

 agree in making it very probable that sable lies near the other end 

 (z. e.y to the right). Sable will he farther to the right than vermilion, 

 for vermilion has been shown elsewhere to give 33 per cent of crossing- 

 over with eosin. The location of sable to the right of vermilion has in 

 fact been substantiated by all later work. 



LINKAGE OF EOSIN, VERMILION, AND SABLE. 



Three loci are involved in the next experiment. Since eosin is an 

 allelomorph of cherry, it should be expected to give with sable the 

 same cross-over value as did cherry. When eosin (red) sable females 

 were crossed to (red) vermiHon (gray) males, the daughters were wild 

 type and the males were eosin sable. Inbred these gave the classes 

 shown in table 11. 



