486 THEOPHILUS S. PAINTER 



surface tension and a flow of the cortical layers of protoplasm 

 toward the cleavage area. 



12. It is pointed out that this nuclear factor is not a new 

 conception, but that its various expressions have been emphasized 

 in turn, by a number of different investigators, working on dif- 

 ferent forms. 



13. Evidence has been given to show that, as far as the cyto- 

 plasm is concerned, the asters play the role of regulative centers 

 during cell division, that is, by forming denser areas they re- 

 strict the action of the nuclear factor to a prescribed area. 



14. The history of the chromosomes is followed. 



15. It is suggested that the 'spinning activities' or 'filose 

 activities' of Cerebratulus eggs is similar to the protoplasmic 

 movement of monaster eggs. In the case of the 'filose activities' 

 described by Mrs. Andrews it seems possible that they are re- 

 sponses of the irritable protoplasm to a stimulus similar to that 

 in the monaster eggs, but coming from a different source. 



LITERATURE CITED 



Andrews, E. A. 1898 Activities of the polar bodies of Cerebratulus. Arch. 



f. Entw. Mech., vol. 6. 

 Andrews, Mrs. G. F. 1897 The living substance as such and as organism. 



Jour. Morph., vol. 12. 

 Boveri, M. 1903 Ueber Mitosen bei einseitiger Chromosomenbindung. Jen. 



Zeitschr., Bd. 37. 

 Boveri, Th. 1888 Zellenstudien II. Jenaische Zeitschr., vol. 22. 



1897 Zur Physiologie der Kern- und Zellteilung. Sitz. Ber. d. Phys.- 



Med. Ges. Wurzburg. 



1900 Zellenstudien IV. Jena. 



1903 Ueber das Verhalten des. Protoplasmas bei monocentrischen 



Mitosen. Sitz. Ber. d. Phys.-Med. Ges. Wurzburg. 



1905 Zellenstudien V. Jena. 

 Butschli, O. 1876 Studien ueber die ersten EntwickeIsungsvo:-gange der 



Eizelle, etc. Abh. d. Senckenb. naturf. Ges., vol. 10. 



1892 Untersuchungen liber mikroskopische Schaume und das Pro- 



toplasmen. Leipzig. 



1900 Bemerkungen ueber Plasmastromungen bei der Zellthfilung. 



Arch. f. Entw. Mech., vol. 10. 

 Coe, W. R. 1899 The maturation and fertilization of the egg of Cerebratulus 



Zool. Jahrb., vol. 12. 

 Conklin, E. G. 1902 Karyokinesis and Cytokinesis. Philadelphia. 



1905 The organization and cell-lineage of the ascidian egg. Jcu 



Acad. Nat, Sci.. Phila. 2d Series, vol. 13. 



