MALE GERM CELLS IN NOTONECTA 99 



2. In all three species all the chromosomes are aggregated 

 during the growth period to form a massive karyosphere, which 

 consists of chromatic bodies embedded in plasmasome material. 

 The precise origin of this body is somewhat difficult to ascertain, 

 but the evidence indicates that it contains at least part of the 

 early spireme. 



3. In the prophases the chromosomes are formed from the kary- 

 osphere, which gives rise to dense chromatic bodies, which form 

 diffuse double threads; these condense to form ring- and cross- 

 tetrads, etc., whose entire history can in some cases be traced. 



4. Mitochondria are present in the form of a flat plate in the 

 early stages, and of spheres and fibers later; the fibers may arise 

 directly from the spheres. The mitochondria are divided en 

 masse with cell division. 



September. 1912 



LITERATURE CITED^ 



Arnold, G. 190S The nucleolus and microchromosomes in the spermatogenesis 

 of Hydrophilus piceus. Arch. f. Zellforsch., Bd. 2. 



Artom, O. 1911. La sistematica del genere Artemia in relazione col numero dei 

 cromosomi, etc. Biol. Centrb., Bd. 31. 



Bateson, W.. and Punnett, R. C. 1911 On the interrelations of genetic fac- 

 tors. Proc. Roy. Soc, vol. 84. 



Baumgartner, W. J. 1904 Some new evidences for the individuality of the 

 chromosomes. Biol. Bull., vol. 8. 



Benda, C. 1902 Die Mitochondria. Ergebn. d. Anat. u. Entw., Bd. 12. 



Bl.\ckman, M. W. 1903 The spermatogenesis of the myriapods. II. Biol. 

 Bull., vol. 5. 



1905 a Ibid. III. The spermatogenesis of Scolopendra heros. Bull. 

 Mus. Comp. Zool. Har. Coll., vol. 48. 



1905 b Ibid. IV. On the karyosphere and nucleolus in the sperma- 

 tocytes of Scolopendra subspinipes. Proc. Am. Acad. Arts and Sci., vol. 

 41. 



1907 Ibid. V. On the spermatogenesis of Lithobius. Ibid., vol. 42. 

 1910 Ibid. VI. An analysis of the chromosome-group of Scolopen- 

 dra heros. Biol. Bull., vol. 19. 



Bonnevie, K. 1907 'Heterotypical' mitosis in Nereis limbata. Biol. Bull., 

 vol. 13. 



Boring, A. M. 1907 A study of the spermatogenesis of twenty-two species of 

 Membracidae, etc. Jour. Exp. Zool., vol. 4. 



1909 A small chromosome in Ascaris megalocephala. Arch. f. Zell- 

 forsch., Bd. 4. 



^ In order to abbreviate the literature list, many papers have been referred to in 

 general, and are not included in the list. 



