m^ VI 



n 



D. melanogaster 

 (triploid) 



XY 



D. funebris 



w 



1 ^^^n 



Race A Race B 



D. pseudo-obscura 



D. miranda 





m . VI 



XY 



D. virilis 





X 



Race A Race B 



D. montium 



Fig. 20. — Somatic chromosome sets of various species of 

 Drosophila ; all male except the triploid D. melanogaster. 

 Genetically active parts of chromosomes black, inert 

 parts stippled. Inversion between D. melanogaster and 

 D. simulans and between the A and B races of D. pseudo- 

 obscura labelled 1, 2, 3, 4. . . . In D. montium the 

 extent of the inert regions is not known so that they have 

 not been indicated. The microchromosomes have been 

 drawn as if they had median spindle attachments, but 

 nothing is really known as to the exact location of the 

 spindle attachments. 



