SOMATIC MITOSES OF THE MOSQUITO 587 



Nevertheless differentiations do not take place in the absence of 

 nuclear material, and it seems probable that the interaction of 

 nucleus and cytoplasm is necessary to the formation of the new 

 cytoplasmic substances which appear in the course of develop- 

 ment." 



SUMMARY 



1. Three pairs of chromatin threads appear in the prophase. 

 The threads are V-shaped and the apices of the V's are directed 

 toward the same pole suggesting the anaphase position (figs. 2 

 to 16). 



2. In the metaphase the threads have shortened and thickened 

 and have become more widely separated. There are three very 

 definite pairs or four long and two shorter chromosomes (figs. 

 17 to 31). 



3. Before the division begins the position of the chromosomes 

 is altered once again and the chromosomes come to lie side by 

 side (figs. 25 and 31). 



4. The spindle fibers are apparently attached to the apices of 

 the V's. 



5. The somatic chromosome number is six, as is that of the 

 spermatogonia and ovogonia. 



6. The number is the same for all the tissue studied. These 

 include nervous tissue, limb buds, intestine, epithelium, ovarian 

 tissue and Malphigian tubules. 



7. The importance of proper fixation has been emphasized. 



BIBLIOGRAPHY 



Conklin, E. G. 1915 Heredity and environment, p. 182. 



Hance, Robert T. 1915 Pollen development in Zebrina pendula with special 



reference to the chromosomes. Bull. Torrey Bot. Club, 42. 



1916 Notes on embedding in paraffin. Trans. Amer. Mic. Soc, 35. 



1917. The fixation of Mammalian chromosomes. Anat. Record. 



April. 

 Hoy, W. E., Jr. 1916 A study of somatic chromosomes. I. Biol. Bull., vol. 



31, no. 5. 

 Metz, Charles W. 1916 Chromosome studies on the Diptera. II. Jour. Exp. 



Zool., vol. 21, no. 2. 

 Morrill, Charles V. 1910 Chromosomes in coroid Hemiptera. Biol. Bull., 



19. 



