THE CELL ASTER 501 



sphere and of the rays, also the hyaline area in the vicinity of the 

 forming polar body, are very fluid. 



9. The aster in its early stage can be made to disappear by 

 churning the cytoplasm with a needle. This causes a reversal 

 of the gel to the sol state. 



10. From a study of cell division in the eggs of Echinarachnius, 

 Cerebratulus, Arbacia and Asterias, it may be concluded that 

 one of the factors concerned lies in a peculiar colloidal property 

 of protoplasm, viz., a periodic reversibihty in its sol and gel 

 states. 



V. BIBLIOGRAPHY 



Barber, M. A. 1914 The pipette method in the isolation of single micro- 

 organisms and in the inoculation of substances into living cells. The 

 Philippine Jour, of Sc, vol. 9, Sec. B., Tropical Medicine, p. 307. 



BtJTSCHLi, O. 1892 Investigations on microscopic foams and on protoplasm. 

 Trans, by E. A. Minchin, 1894. London: A. and C. Black. 



Chambers, Robert, Jr. 1915 Microdissection studies on the physical prop- 

 erties of protoplasm. Lancet-clinic, Mar. 27, 1915, Cincinnati. 

 1917 a Microdissection studies, I. The visible structure of cell pro- 

 toplasm and death changes. Amer. Jour. Physiol., vol. 43, p. 1. 

 1917 b The microdissection method. Biol. Bull., vol. 32. 



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

 Zool. Jahrb., Bd. 12. 



CoNKLiN, E. G. 1902 Karyokinesis and cytokinesis in the maturation, fertiliza- 

 tion and cleavage of Crepidula and other gastropods. Jour. Acad. 

 Nat. Sci., Phila., vol. 12, ser. 2. 



1905 The organization and cell lineage of the Ascidian egg. Jour. 

 Acad. Nat. Sci., Phila., vol. 13, ser. 2. 



1912 Experimental studies on nuclear and cell division in the eggs of 

 Crepidula. Jour. Acad. Nat. Sci., Phila., vol. 15, ser. 2, p. 503. 



Fischer. Alfred 1899 Fixierung, Farbung und Bau des Protoplasmas. Jena, 

 G. Fischer, 362 pp. 



Gaidukov, N. 1910 Dunkelfeld-Beleuchtung und Ultra-Mikroskopie in der 

 Biologic und in der Medizin. Jena, G. Fischer, 84 pp. 



Hardy, W.B. 1899 Structure of cell protoplasm. Jour. Physiol., vol. 24, p. 158. 



Hartog, Marcus 1905 The dual force of the dividing cell. Part I. The 

 achromatic spindle figure illustrated by magnetic chains of force. 

 Proc. Roy. Soc, London, vol. 76. 



Hatschek, Emil 1913 An introduction to the physics and chemistry of colloids. 

 London: Churchill. 



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

 changes in the egg of Arbacia. Biol. Bull., vol. 29, p. 149. 



t 



