594 



[ Vol. L 



sociates with its corresponding maternal mate. (See 

 Metz, '16, p. 251.) 



Type C 



Eepresented by 

 DrosophUa ornatipennis Will. Cuba. (Metz, '16, 

 Fig. 21.) 



Scaptomyza adust a Loew. New York. (Fig. 10; 

 Metz, '16, Fig. 22.) 

 Type C corresponds to type IV of my previous paper 

 ('14), but the single species formerly referred to it has 

 been transferred to type E. Chromosome groups of type 

 C are composed of one large V-shaped pair, one long, 

 straight sex chromosome pair, two shorter rod-like pairs 

 and one small w-pair. In both species spermatogonial 

 figures show a noticeable inequality between X and Y; 

 thus identifying the sex chromosomes. 



Type D 



Eepresented by 



DrosophUa tri punctata Loew. New York. (Metz, 

 '14, Figs. 21-26.) 



Type D corresponds to type V of my previous paper 

 ( '14) and includes only one species. It differs from type 

 C in lacking the w-ehromosome pair, and in sex chromo- 

 some relations. X and Y are apparently equal in size 

 and similar to the rod-like euchromosomes. Their iden- 

 tification is based solely upon their precocious contrac- 

 tion in prophase (see Metz, '14, p. 52), and hence may be 

 held with some reserve, but from analogy with species 

 of types A and C it seems highly probable that the iden- 

 tification is correct. 



Many preparations have been made from material of 

 this species in an attempt to discover an w-chromosome 

 pair such as is found in most other species of DrosophUa, 

 but although stocks have been obtained from several 

 localities and various methods of fixation have been used 

 no trace of the pair has been observed. 



