No. 6-W] MUTANT CHARACTERS IN DROSOPHILA 



213 



means of the sex-linked characters and their linkage re- 

 lations. 



The stock of D. ivillistoni which we have used was 

 brought from Cuba in 1915, and was kept in the labora- 

 tory without being studied until 1919 when the present 

 work began. 



In making the tests for linkage and in calculating cross- 

 over values, the usual procedure has been followed.- We 

 have been concerned particularly with determining the 

 relative order of the genes and the approximate amount 

 of crossing over between them, but not with obtaining 

 exact crossover values. In consequence, the " chromo- 

 some map given here is to be considered as indicating 

 only the approximate location of the respective genes. 



In presenting the data, the mutant types are described, 

 not in chronological order, but in such a way as to follow 

 the serial order of the genes on the chromosome map. 

 All of the sex-linked characters are recessive. The data, 

 on the origin of mutants are necessarily imperfect, and 

 in some cases are very meager, owing to the fact that 

 many of the mutants appeared in stock cultures, mass 

 cultures, etc., for which no complete records were taken. 

 In such cases the available data are given briefly under 

 the appropriate headings. 



We are indebted to Mr. D. E. Lancefield for carrj^ing 

 out some of the early experiments, and for finding the 

 mutants rimmed" and ''nicked." Similarly, we are in- 

 debted to Miss Ruth Ferry for the mutant " yellow " and 

 for carrying out the experiments involving " yellow."" 

 To Dr. A. H. Sturtevant we owe many valuable sugges- 

 tions regarding the comparison of mutant characters in 

 D. U'illistoni with those in D. melanogaster and D. simu- 

 lans. We are also indebted to the following persons for 

 making the accompanying drawings: Miss Ruth Lincks 

 — Figs. 1, 3, 7, 8 ; Mrs. D. B. Young — Figs. 2, 4, 5, 6, 17 ; 

 Miss E. M. Wallace — Fig. 9, and Miss E. D. Mason — 

 Figs. 10-16. 



