Metz and IMoses : Chromosomes 



197 



4)X ^ (L JX% JJ% 



II 



II 



II 



II 





\\ II 

 II , 





II 



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II 





v^. 



r« ^-^^"^ 



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CHROMOSOME PATTERNS IN DROSOPHILA 



Figure 3. Diagrams of the known types of chromosome groups in the Drosophilinae. 

 All but Type H are found within the genus Drosophila. XX indicates sex-chromosomes. 

 Notice the similarity between Types A, B, and M. Types A and M were confused for a 

 time, as the absence of the dot-like chromosome may be contributed to faulty staining tech- 

 nique. Later it was found that the sex-chromosomes were V-shaped in M instead of rod- 

 like as in A. The great majority of species belong in Type A or Type F. 



Note: We are indebted to Miss E. M. Lord for making the drawings used in this article. 



Type E 



D. melanica Sturt. 



Type F 

 D. cardini Sturt. 

 D. ramsdcni Sturt. 



/). iiiiillcri Sturt. (rcplcta variety a) 

 D. sinulis Will. 



D. tripiiiictata Loew. (modcsta) 

 D. virilis Sturt. 



D. species? (European, resembles D. ob- 

 scura ; not in previous list) 



Type G 

 D. fiiiicbris Fabr. 



Type H 

 Gladocliaeta nebulosa Coq. 



Type I 

 D. repleta Woll. (rcplcta variety b). 

 D. hydei Sturt. 



Type J 

 D. obscura Fall. (Oregon) 



Type K 

 D. affiuis Sturt. 



Type L 

 D. caribbca Sturt. 



Type M 

 D. zviUisto)ii Sturt. (pallida) 



The Sex-Chromosomes 



The diagrams in Figure 2 are based 

 on the chromosome groups of the 

 females. The sex-chromosomes here 

 are represented by the lowermost pair 

 of the group and are marked XX 

 wherever they have been identified ; 

 but they have not been identified in all 

 cases. One reason for this is that 

 some of the species do not exhibit a 

 conspicuous dimorphism between the 

 X and Y chromosomes in the male 

 (which is the criterion usually used 

 for identification). In addition it is 

 usually more difficult to obtain figures 

 of the male groups than of the female 

 groups in this material, particularly 

 from adult flies, and consequently we 

 lack male figures of some of the less 

 common or less easily reared species. 



The present section includes the 

 known evidence on the sex-chromo- 

 somes and also a statement indicating 

 where the evidence is doubtful and 

 where it is lackin'j:. 



