524 P. W. WHITING 



1. INTRODUCTION 



On account of the contradictory statements published in regard 

 to the cytological conditions of the common house mosquito, 

 Culex pipiens L., it was thought worth while to investigate the 

 matter thoroughly in order to find out the cause of disagreement 

 and to discover the true conditions. This has seemed of especial 

 interest in view of the extensive genetic work that is being done 

 on one of the higher Diptera, Drosophila ampelophila Loew. 



While certain other orders of insects have been well investi- 

 gated cytologically, the published work on the Diptera is very 

 meager. It consists of two papers on mosquitoes by Stevens 

 ('09 and '11), one by the same author on nine species of Myo- 

 daria ('08), a paper on Culex pipiens by Lomen ('14), another 

 by Taylor ('14), and a paper on twelve species of Drosophila by 

 Metz ('14). Besides these there are two short reviews, one by 

 Metz ('16), and one by Dehorne ('14), and a genetic paper by 

 Bridges ('16) dealing with non-disjunction of the sex chromo- 

 somes in gametogenesis of Drosophila ampelophila and figuring 

 and describing the diploid complexes. 



It was thought best to make a thorough study of the sper- 

 matogenesis of Culex pipiens and a comparative study of condi- 

 tions in the ovary and somatic tissue. By reason of improved 

 technique and the encouragement and criticism of Dr. C. E. 

 McClung, Dr. D. H. Wenrich, and Miss E. Eleanor Carothers, I 

 have been enabled to make considerably more out of the mate- 

 rial than was at first expected. 



A discussion of technique, together with a criticism of the 

 literature, will be reserved until after the descriptive part of 

 the paper. It is believed that the contradictory results obtained 

 by the various investigators have been largely due to differences 

 of technique and it is therefore desirable to discuss these matters 

 after presenting my own results. It may merely be stated here 

 that Flemming's stronger fluid has been used as a fixative except 

 where otherwise mentioned. Culex pipiens may be bred in large 

 numbers throughout the winter months and quantities of mate- 

 rial obtained at all times for study. 



