THE CHROMOSOMES IN THE GERM-CELLS OF CULEX 



N. M. STEVENS 



Bryn Maivr College 

 With Fifty-two Figures 



In the summer of 1905, Miss Boring and I collected material 

 for the study of the spermatogenesis of the mosquito, but the germ- 

 glands proved not to be sufficiently well fixed. In 1907 I spent 

 several days studying aceto-carmine preparations from the larvae 

 and pupae of some California mosquitoes. Naturally I expected 

 to find one or more heterochromosomes, but nothing of the kind 

 could be detected either in the growth stages of the spermatocytes 

 or m the maturation divisions. The number ot chromosomes was 

 small, only three in one species and tour in the other, but it was not 

 an easy matter to determine whether or not the pairs of univa- 

 lents were exactly equal. 



In October of this year (1909) I accidentally discovered an 

 abundance of larvae and pupae of Culex (sp.' not determined, prob- 

 ably C. pungens), in a small pond where I was able to collect 

 the material up to November 22. This time I determined the 

 location of the testes and ovaries, in the third segment from the 

 end of the tail — removed the anterior segments, and secured good 

 fixation in Flemming's fluid and fairly good in Gilson's mercuro- 

 nitric. The larger part of the material was dissected and the germ- 

 cells studied in aceto-carmine preparations. With careful sealing 

 it has been found that these slides can be kept in usable condition 



' April 7, 191 o. It is now quite certain that pupa of two species were used in this work. Al! 

 of the material that can be obtained from the same pool this season will be examined with a view 

 to determining the conditions in the germ cells of each species breeding there. A species of Anopheles 

 with 6 chromosomes in the spermatocytes has already been found. 



