No. 598] CHROMOSOME STUDIES ON THE DIPTERA 597 



included in the present review because of its obvious rela- 

 tionship to the true Drosophilas. The type of chromo- 

 some group which it represents is the only one of the 

 twelve not thus far found in some species of Drosophila, 

 and its general similarity to some of the Drosophila types 

 is marked. Female groups consist of three similar pairs 

 of long, V-shaped chromosomes and one small pair of 

 »/-<'hr<>mi>somos. Infortimately the species hreeds very 

 poorly in confinement and no male preparations were 

 secured. It is almost certain, however, that one of the 

 long pairs is the sex chromosome pair. 



Type I 



Represented by 



Drosophila repleta Woll., variety b. New York, 

 Massachusetts, California. (Figs. 17 and 18; 

 Metz, '16, Figs. 39-41.) 



In my 1914 paper D. repleta was referred to the type 

 corresponding to F of the present study, but it is now 

 evident that two very similar but distinct varieties of the 

 species occur, characterized, among other things, by de- 

 cidedly different sex chromosomes. In one, the sex 

 chromosomes are short and rod-like in the female and 

 presumably so in the male, while in the other they are 

 long and V-shaped in the female and markedly unequal in 

 the male. The latter represents the present type L The 

 difference between the two may be readily appreciated 

 by an examination of diagrams F and /. Although it 



