THE AMERICAN NATURALIST [Vol. LII 



tary to make sure that the new gene was at the rudimentary 

 locus. Since homozygous rudimentary females show a high de- 

 gree of sterility, the rudimentary stock is kept by crossing it to 

 forked and using normal-winged females that are heterozygous 

 for both rudimentary and for forked. One of the new rudimen- 

 tary males was crossed to such a heterozygous female and the 

 new rudimentary was shown to be an allelomorph of the old. as 

 both rudimentary sons and daughters were obtained in practi- 

 cally equal numbers. The new rudimentary stock resembled the 

 old as regards the sterility of the homozygous females. Miss C. 

 J. Lynch in this laboratory tested several and reported that they 

 showed the same high degree of sterility. Sim-e the new char- 

 acter has the same appearance as old rudimentary, this seems to 

 be merely the reappearance of that gene. 



In this case it is clear that the change occurred in one of the 

 maternal sex-chromosomes which already carried three sex- 

 linked genes. The linkage relations of the new gene to these 

 maternal genes make its origin in the maternal chromosome cer- 

 tain. Moreover, the male could have received his sex-chromo- 

 some only from his mother, as otherwise he would have been an 

 XO male and would have been sterile. 5 The fly could not be ac- 

 counted for on the assumption of contamination, as there are no 

 flies of that particular constitution in the laboratory. The muta- 

 tion was from the normal gene at the rudimentary locus. The 

 appearance of only one individual indicates that the change oc- 

 curred late in the history of the egg. 



Summary 



1. Two mutations have occurred at the white locus in the nor- 

 mal red gene, giving rise to a reappearance of white and to a new 

 gene which produces an eye color called coral. 



2. Coral is the eighth member of the multiple allelomorph 

 series at the white locus. 



3. Rudimentary reappeared as a change from the normal gene 

 at that locus in a maternal chromosome. 



LITERATURE CITED 



Bridges, C. B. 



1916. Non-disjunction as Proof of the Chromosome Theory of 

 Heredity. Genetics, I, 1-52, 107-163. 

 Hyde, Roscoe E. 



1916. Two New Members of a Sex-linked Multiple Allelomorph Sys- 



