2l6 N. M. Stevens 



that parasynapsis of homologous chromosomes occurs in the tel- 

 ophase of each mitosis of the germ-cells, and that this intimate 

 relation of the paternal and maternal members of the pairs per- 

 sists from one mitosis to the next, when in the oogonia and sperma- 

 togonia, each chromosome divides longitudinally, but in matura- 

 tion the two members of a pair separate and go to different cells. It 

 is of especial interest to see in Culex a perfectly clear case of para- 

 synapsis change in some cases to an equally clear case of telosvn- 

 apsis before metakinesis, while intermediate ring-stages and cases 

 of overlapping ends also occur. 



SUMMARY 



1 The number of chromosomes in Culex sp. is six in oogoma and 

 spermatogonia and three in the spermatocytes. 



2 There is some evidence that a small unequal pair of hetero- 

 chromosomes is combined with a larger equal pair of chromosomes. 



3 During the synizesis stage, the staining quality of the plasmo- 

 some changes in such a way as to indicate that it has received 

 chromatin material from the chromatin threads wound about it. 



4 Parasynapsis occurs in each cell-generation of the germ- 

 cells, the homologous maternal and paternal chromosomes being 

 paired in telophase and remaining so until the metaphase of the 

 next mitosis. 



5 Parasynapsis of homologous chromosomes often changes 

 to telosynapsis in the metaphase of the first spermatocyte. 



Bryn Mawr College 

 December 20, 1909' 



BIBLIOGRAPHY 



Boring, A. M. '07 — A Study of the Spermatogenesis of Twenty-two Species of 



Membracidae, Jessidae, Cercopidae and Fulgoridae. Jour. Exp. Z06I., 



vol. 4. 

 BucHNER, P. '09 — Das accessorische Chromosom in Spermatogenese und Ovo- 



genese der Orthopteren, zugleich ein Beitrag zur Kenntnis der 



Reduktion. Arch. f. Zellforschung., vol. 3. 

 Dederer, p. H. '07 — Spermatogenesis im Philosamia cynthia. Biol. Bull., vol. 



'Received for publication Jan. 15, igio. 



