STUDIES ON GERM CELLS 489 



the entire germ cell cycle. It seems probable, however, that the 

 particular kind of cytoplasm (germ-plasm) marked by the pres- 

 ence of these bodies is continuous throughout the germ cell cycle. 

 In some animals (e.g., Miastor, fig. 32) it constitutes the entire 

 substance (with the exception of the nucleus) of the primordial 

 germ cell; this is also true in other animals, but, as shown in 

 figure 17, a succession of cleavage divisions occurs before the 

 germ-plasm is entirely separated from the somatic-plasm. The 

 nature of the Keimbahn-determinants is uncertain, but their 

 origin from metanucleoli, nurse cells, and possibly the nutritive 

 stream suggests that they may play a role in the nutrition of 

 the germ cells during the period extending from their segregation 

 until the formation of the definitive germ glands (pp. 482-485). 



Ann Arbor, Michigan 

 November 16, 1913 



LITERATURE CITED 



Allen, B. M. 1906 The origin of the sex-cells of Chrysemys. Anat. Anz., Bd. 



29. 



1907 a An important period in the history of the sex-cells of Rana 



pipiens. Anat. Anz., Bd. 31. 



1907 b A statistical study of the sex-cells of Chrysemys marginata. 



Anat. Anz., Bd. 30. 



1909 The origin of the sex-cells of Amia and Lepidosteus. Anat. 



Rec, vol. 3. 

 Amma, K. 1911 Ueber die Differenzierung der Keimbahnzellen bei den Cope- 



poden. Arch. f. Zellforsch., Bd. 6. 

 Ancel, p. 1903 Histogenese et structure de la glande hermaphrodite d' Helix 



pomatia. Arch. Biol., t. 19. 

 Balbiani, E. G. 1864 ISur les mouvements qui se manifestant dans la tache 



germinative chez quelques animaux. C. R. Soc. Biol., Paris. 



1866 Sur la reproduction et I'embryogenie des pucerons. Compt. 



Rend. Acad. Science Paris, tom. 62. 



1869-72 Memoire sur la generation des Aphides. Ann. Sci. Nat. 



Paris, 5 serie, tom. 11, 1869; tom. 14, 1870; tom. 15, 1872. 



1882 Sur La signification des cellules polaires des insects. Compt. 



Rend. Acad. Sci. Paris, tom. 95. 



1885 Contribution a I'etude de la formation des organes sexuelles chez 



les insects. Recueil Zool. Suisse, tom. 2. 

 Bambeke, C. van 1893 Contribution a I'histoire de la constitution del'oeuf. 2. 



Elimination d'elements nucleaires dans I'oeuf ovarien de Scorpaena 



scrofa. Bui. Acad. Belg., (3) t. 25. 



1897 L'oocyte de Pholcus phalangioides Fuessl. Verh. d. anat. Gesell., 



elfte Versammlung. 



