CELL DIVISION^SPINDLE IN SEA-URCHIN EGGS 237 



a. It can be most closely imitated by an abstraction of water. 

 Cytoplasmic gels produced by hypertonic solutions on unfer- 

 tilized eggs behave toward cold and ether much like the normal 

 gel of the fertilized egg. Cytoplasmic gels produced by acid or 

 by distilled water do not exhibit this resemblance. 



b. Entrance of water into the fertilized egg reverses the normal 

 cytoplasmic gelation. 



LITERATURE CITED 



Albrecht, E. 1898 Untersuchungen zur Struktur des Seeigeleies. Sitzungs- 



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 VAN Beneden, E. 1875 La maturation de I'oeuf, la fecondation et les prem- 

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2meser.,T. 40. 

 Chambers, R. 1917 Microdissection studies. II. The cell aster; a reversible 



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 Flemming, W. 1882 Zellsubstanz, Kern- und Zelltheilung. Leipzig 1882 (see 



especially pp. 206-208). 



1891 tjber Theilung und Kernformen bei Leukocyten, und iiber deren 



Attraktionspharen. Arch. f. mik. Anat., Bd. 37; S. 249-298. 

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genie chez divers animaux. Mem. d. 1. Soc. de Phys. et d'Hist. Nat. 



de Geneve, T. 26. 

 Heilbrunn L. V. 1915 Studies in artificial parthenogenesis. II. Physical 



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1917 An experimental study of cell division. Proc. Amer. Soc. Zool., 



Anat. Rec, vol. 11, pp. 487-489. 

 Hertwig, O. 1890 Experimentelle Studien am tierischen Ei, vor, wahrend, and 



nach der Befruchtung. Jenaische Zeitschr., Bd. 24, S. 268-313. 

 Levi, G. 1916 La costituzione del protoplasma studiata su cellule viventi 



coltivate 'in vitro.' Archivio di Fisiologia, T. 14, pp. 101-112. 

 Loeb, J. 1892 Investigations in physiological morphology. III. Experiments 



on cleavage. Jour. Morph., vol. 7, pp. 253-262. 

 Norman, V/. W. 1896 Segmentation of the nucleus without segmentation of 



the cytoplasm. Arch. f. Entwicklungsmechanik, Bd. 3, S. 106-126. 

 Spek, J. 1918 Oberflachenspannungsdifferenzen als eine Ursache der Zellteil- 



ung. Arch. f. Entwicklungsmechanik, Bd. 44, S. 5-113. 

 Wilson, E. B. 1901 Experimental studies in cytology. II. Some phenomena 



of fertilization and cell-division in etherized eggs. III. The effect on 



cleavage of artificial obliteration of the first cleavage furrow. Arch. 



f. Entwicklungsmechanik, Bd. 13, S. 353-395. 



