CHROMOSOME STUDIES IN THE DIPTERA 



I. A PRELIMINARY SURVEY OF FIVE DIFFERENT TYPES OF CHROMO- 

 SOME GROUPS IN THE GENUS DROSOPHILA 



CHARLES W. METZ • 



From the Department of Zoology, Columbia University 



DIAGRAM AND TWENTY-SIX FIGURES (pLATE) 



To the student of chromosomes and chromosome behavior a 

 cytological study of the Diptera presents many features of inter- 

 est. Some of these have been described or mentioned by Miss 

 N. M. Stevens in connection with her work on the sex chromo- 

 somes,^ but aside from this I know of no serious attempts at such 

 a study. When compared with the detailed and critical works on 

 the chromosomes of the Hemiptera, Orthoptera, and Coleoptera, 

 this lack of knowledge of the Diptera is surprising, and can be 

 explained only by the fact that the latter are in many ways un- 

 satisfactory objects for cytological study. The difficulties in 

 such a study are admittedly numerous, but notwithstanding, 

 much can be accomplished, and the interest of the questions in- 

 volved seems to me to more than justify the extra effort expended 

 in their investigation. 



For this reason a series of such studies has been undertaken, the 

 extent of which will depend upon the time and facilities available. 

 Some are under way at present and others will be taken up subse- 

 quently. The results I hope to present in a series of papers, to 

 which the present is introductory. 



1 So far as known to the writer, the papers of Dr. Stevens are the only ones 

 dealing with the chromosomes of the Diptera. They are four in number: The 

 chromosomes of Drosophila ampelophila. 1907. Proc. VII Internat. Zool. 

 Cong. A study of the germ cells of certain Diptera, with reference to the 

 heterochromosomes and the phenomena of synapsis. 1908. Jour. Exp. Zool., vol. 

 5, pp. 359-374. The chromosomes in the germ cells of Culex. 1910. Jour. Exp. 

 Zool., vol. 8, pp. 207-217. Further studies on the heterochromosomes of the 

 mosquitoes. 1911. Biol. Bull., Vol. 20, p. 109. 



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