ASSOCIATION OF CHROMOSOMES IN DIPTERA 217 



question is not directly involved in the present paper. In re- 

 gard to the problem of synapsis the pairing phenomena in diploid 

 cells, including final spermatogonia, clearly demonstrate that 

 a side by side approximation of corresponding chromosomes (the 

 essential feature of synapsis), actually does occur, although in 

 this case it is not connected with maturation. 



Throughout the course of this study I have profited greatly 

 by the counsel of Prof. E. B. Wilson, under whose direction the 

 work was begun, and to whom I have become increasingly 

 indebted for many kindnesses. 



MATERIAL AND METHODS 



My observations are based upon a study of the chromosomes 

 in about eighty species of Diptera, representing thirty-five genera 

 and fifteen families, as given in the following synopsis. 



Okthorrapha 



Nemocera 

 Culicidae 



Culex pipiens Linne. 

 Brachycera 



Stratiomyidae 



Ptecticus triviltatus Say. 

 Asilidae 



Asilus sericeus Say. 



Asilus lecythus Walk. 



Asilus notatus Wied. 



Asilus novae scotiae Macq. 



Asilus sadytes Walk. 



Ommatius marginellus Fabr. 



Leptogaster badius Loew. 



Erax aestuans Linne. 



Erax rufibarbis Macq. 



Dasyllis grossa Fabr. 



Dasyllis thoracica Fabr. 



Deromyia winthemi Wied. 

 Bombyliidae 



Anthrax lateralis Say 



Anthrax sinuosa Wied. 

 . Spogostylum simson Fabr. 



