NEW DATA. 51 



and miniature is over 30 per cent, the lethal factor must lie between 

 eosin and miniature, somewhat nearer to eosin. It is impossible at 

 present to locate lethal 2 accurately because of a real discrepancy in 

 the data, which makes it appear that lethal 2 extends for a distance 

 of about 5 units along the chromosome from about 10 to about 15. 

 Work is being done which it is hoped will make clear the reason for 

 this. For the present we may locate lethal 2 at the midpoint of its 

 range, or at 12.5. 



CHERRY. 



(Plate II. figure 9.) 



The origin of the eye-color cherry has been given by Safir (Biol. 

 Bull., 1913). 



Cherry appeared (October 191 2) in an experiment involving vermilion 

 eye-color and miniature wings. This is the only time the mutant has 

 ever come up, and although several of this mutant (males) appeared 

 in Safir's experiment, they may have all come from the same mother. 

 It is probable that the mutation occurred in the vermilion stock only a 

 generation or so before the experiment was made, for otherwise cherry 

 would be expected to be found also in the vermilion stock from which 

 the mothers were taken; however, it was not found. 



A SYSTEM OF QUADRUPLE ALLELOMORPHS. 



Safir has described crosses between this eye-color and red, white, 

 eosin, and vermilion. We conclude for reasons similar to those given 

 by Morgan and Bridges (Jour. Exp. Zool., 1913) for the case of white 

 and eosin, that cherry is an allelomorph of white and of eosin. This is 

 not the interpretation followed in Safir's paper, where cherry is treated 

 as though absolutely linked to white or to eosin. Both interpretations 

 give, however, the same numerical result for each cross considered by 

 itself. Safir's data and those which appear in this paper show that 

 white, eosin, cherry, and a normal (red) allelomorph form a system of 

 quadruple allelomorphs. If this interpretation is correct, then the 

 linkage relations of cherry should be identical with those of white or of 

 eosin. 



LINKAGE OF CHERRY AND VERMILION. 



The cross-over value for white (eosin) and vermilion, based on a 

 very large amount of data, is about 31 units. An experiment of our 

 own in which cherry was used with vermilion gave a cross-over value 

 of 31 units, which is a close approximation to the cross-over value of 

 white and vermilion. The cross which gave this data was that of a 

 cherry vermilion (double recessive) male by wild females. The FI 

 wild-type flies inbred gave a single class of females (wild-type) and the 

 males in four classes which show by the deviation from a I : I : I : I 

 ratio the amount of crossing-over involved. 



