CHROMOSOME STUDIES ON THE DIPTKUA 



III. Additional Types of Cjtromoso.m k (Jroups in the 



DEOSOPHILID.E 

 CHAELES W. METZ 

 Station fob Experimental Evolution, Cold Spring Harbor, N. Y. 



In connection with other work on the Drosophilas I 

 have for some time been engaged in a comparative study 

 of their chromosomes, with especial reference to possible 

 phylogenetic relationships between different species. A 

 short preliminary report of this study was published two 

 years ago (Metz, '14) after five types of chromosome 

 groups had been found among eleven species. More re- 

 cently I have studied fifteen additional species of Dro- 

 sophila, one of Cladochceta and two of Scaptomyza (re- 

 lated genera), and have found several more types of 

 chromosome groups. Altogether twelve main types and 

 several sub-types have been identified — a series more ex- 

 tensive, I believe, than any heretofore recorded among 

 allied species. Of these twelve types all but one are 

 represented in the genus Drosophila. 



The study has not yet advanced far enough to fulfil the 

 purpose for which it was originally undertaken, but in 

 view of the widespread interest recently attracted to the 

 Drosophilas as objects of genetic research it seems desir- 

 able briefly to describe the chromosomes of the species 

 thus far examined without awaiting the completion of the 



