THE SEX-LINKED GROUP OF MUTANT CHAR- 

 ACTERS IN DROSOPHILA WILLISTONI 



EEBECCA C. LANCEFIELD AND CHAELES W. METZ 

 Station for Experimental Evolution, Cold Spring Harbor, X. Y. 



Introduction 



The present work was undertaken for the purpose of 

 comparing the genetical behavior of the fruit-fly Broso- 

 phila willistoni with that of Drosophila melanogaster and 

 other members of the genus. It deals with the 28 sex- 

 linked mutant characters thus far studied. The non-sex- 

 linked characters will be considered in another paper. 



Drosophila willistoni Sturtevant (D. pallida Williston)* 

 is not unlike the well-known D. melanogaster in habits 

 and superficial appearance, but a detailed examination 

 reveals numerous features in which it differs from melor- 

 nogaster. Among these are the following: (1) absence 

 of sex combs in the male, (2) six instead of eight rows 

 of acrostichal hairs on the thorax, (3) smaller size and 

 more slender form, (4) vermilion instead of red eye color, 

 and (5) narrow instead of broad bands on the abdomen. 



This species has been chosen for the present study be- 

 cause it is one of the species having the same general 

 type of chromosome group as D. melanogaster. It will be 

 recalled that within the genus Drosophila at least eleven 

 different types of chromosome groups are represented 

 (Metz, 1916). The most common type is that called type 

 A (Fig. A, present paper), which is found in 13 of the 

 29 species studied. In these 13 species (which include 

 melanogaster and ivillistoni), the chromosome groups are 

 so much alike as to suggest that similar chromosomes 

 are homologous and carry homologous groups of genes 

 throughout. On the other hand, the species themselves do 

 not form a restricted taxonomic group, but seem to be 



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