196 



The Journal of Heredity 



serve not only for the present purpose 

 but also for ready reference in the 

 future. 



Description of Different Types of 



Chromosome Groups in the 



Drosophilinae 



The principal known types of chrom- 

 osome groups in the Drosophilinae have 

 been described and figured in earlier 

 papers,* ^- ^' ^' ^' but more recent obser- 

 vations necessitate several corrections 

 and changes, as well as additions to 

 the earlier lists. It is also possible 

 now to attach the proper specific names 

 to some of the species not identified 

 before, for Sturtevant has recently 

 published a full taxonomic account of 

 the group. ^t 



The material upon which cytological 

 studies have been made includes twenty- 

 seven species of Drosophila, two of 

 Chymomyza, two of Scaptomyza, one 

 of Mvcodrosophila and one of Clado- 

 chaeta — thirty-three in all. Among 

 these species thirteen types of chromo- 

 some groups have been found as shown 

 diagramatically in Figure 2. All of 

 these but one (type H) are found 

 within the genus Drosophila. It should 

 be stated at the outset that our cytolog- 

 ical knowledge of some of these spe- 

 cies is not extensive, and minor modi- 

 fications may be found to separate the 

 chromosome groups of some species 

 now put under one type ; but we be- 

 lieve that in all of the species included 

 bere the chromosome groups are es- 

 sentially as given. 



The Diptera are particularly favor- 

 able for a comparative study of this 

 kind because of the fact that the 

 chromosomes are arranged in pairs in 

 an almost diagrammatic fashion in the 

 diploid cells, somatic as well as germ- 

 inal. In other words, homologous 

 chromosomes tend to associate and re- 

 main associated throughout develop- 



ment. This association is indicated by 

 the camera lucida drawings published 

 in earlier papers (1. c.) and by the 

 accompanying photographs (Figure 

 1 ).i The diagrammatic representa- 

 tions in Figures 2 and 4, therefore, 

 are not as highly schematized as might 

 be imagined. In most respects they re- 

 semlile the actual figures seen under 

 the microscope. 



The thirteen types of chromosome 

 groups (Figure 2) are not equally com- 

 mon among the species studied, but are 

 for the most part represented by only 

 one species each, with the bulk of the 

 species falling under three main types. 

 The distri1)ution is indicated in the 

 following list. 



List of Species Arranged According to 

 Chromosome Resemblance 



In this list the names in parenthesis 

 are those given in the list published in 

 1916° and subsequently changed. We 

 are indebted to Dr. A. H. Sturtevant 

 for the specific determination in most 

 cases. 



Type A 



Drosophila busckii Coq. 



D. bromcliac Sturt. 



D. florae Sturt. 



D. viclaiiogasfcr Meig. ( aint'clophila)^ 



D. ncbulosa Sturt. (limbata) 



D. qiiinaria Loew. 



D. robitsfa Sturt. 



D. saltans Sturt. 



D. shnulans Sturt. (not in earlier list) 



Chymomyza amocna Loew. {Drosophila 

 amocna) 



Chymomyza procncmis Will. {Drosophila 

 procncmis) 



Mycodrosophila dimidiafa Loew. {Droso- 

 phila dimidiafa) 



Scaptomyza gramiuuni Fall. 



Type B 

 D. carlci Sturt. 



Type C 

 D. calloptcra Schin. {ornatipciinis) 

 Scapto7nyza adusta Loew. 



Type D 



D. iiuiiiii/raiis Sturt. {tripunctata) 



♦For Numbered References, see "Literature Cited" at end of article. 



fThc chromosomal characteristics are briefly reviewed in this also. 



JThe drawings in Figure :', of the present paper arc from smear preparations in which 

 the cells have been flattened and the chromosomes disarranged somewhat, hence the pairing is 

 not so obvious. 



§Names in parenthesis are those given in previous list (Metz 'Kib), and subsequently 

 changed. 



