404 Edmund B. Wilson. 



chromatin elements is thus reduced to one half the spermatogonia! 

 number. In the second maturation-division the asymmetrical 

 dyad separates into its two unequal constituents, the larger one 

 passing to one pole and the smaller one to the other pole ot the 

 spindle, while the other dyads divide equally. 



4. In all the forms excepting Nezara the spermatogonia 

 possess but one microchromosome (the small idiochromosome), 

 while in Nezara two equal microchromosomes are present as in 

 forms like Anasa which possess an accessory chromosome. 



5. In the primary synapsis the idiochromosomes may unite to 

 form a bivalent body or may remain separate. In the former case 

 the bivalent body condenses to form a single chromosome-nucleolus 

 that persists throughout the whole growth-period, but again 

 separates into its univalent constituents before the first mitosis 

 (directly proved in Brochymena, inferred in the other forms). 

 If the idiochromosomes fail to unite in the primary synapsis, 

 they remain separate through the growth-period in the form of 

 chromosome-nucleoli. In either case the idiochromosomes divide 

 separately in the first mitosis. • 



6. In Lygaeus the large idiochromosome has in the synaptic 

 and early post-synaptic periods the form of a long longitudinally 

 split thread which afterward condenses into a hollow spheroidal 

 chromosome-nucleolus. 



Zoological Laboratory, Columbia University, 

 May 5th, 1905. 



WORKS CITED. 



BoNNEViE, K., '05. — Das Verhalten des Chromatins in den Keimzellen ente- 



roxenos ostergreni. Anat. anz., xxvi, 13, 14, 15. 

 Gross, J., '04. — Die Spermatogenese von Syromastes marginatus; Zool. Jahrb., 



Anat. u. Ontog., xx, 3. 

 Montgomery, T. H., '98. — The Spermatogenesis in Pentatoma, etc. Zool. 

 Jahrb., Anat. u. Ontog., xii. 

 '01, I. — A Study of the Chromosomes of the Germ-cells of Metazoa. 



Trans. Amer. Phil. Soc, xx. 

 '01, 2. — Further Studies on the Chromosomes of the Hemiptera heterop- 



tera. Proc. Acad. Nat. Sci., Phil., March, 1901. 

 '04. — Some Observations and Considerations upon the Maturation 

 Phenomena of the Germ-cells. Biol. Bull.j vi, 3, Feb. 



