THE FORMATION OF THE ASTER IN ARTIFICIAL 

 PARTHENOGENESIS.* 



By ROBERT CHAMBERS. 

 {From the Cornell University Medical College, New York.) 



(Received for publication, May 24, 1921.) 



In normally fertilized eggs the development of the aster is attrib- 

 uted to a substance carried into the egg by the spermatozoon. The 

 aster first makes its appearance in the form of diminutive radiations 

 surrounding the neck-piece of the spermatozoon within a few minutes 

 after it has entered the egg. The writer^ has shown that the formation 

 of the radiations is accompanied by a jellying of the cytoplasm of 

 the egg. The jellying process extends more and more as the aster 

 increases in size and the entire egg becomes involved when the center 

 of the aster comes to occupy the center of the egg. 



The formation of the aster is accompanied by an increase in size 

 of a hyaline area in its center. This is Wilson's hyaloplasm-sphere^ 

 also called centrosphere and astrosphere by other investigators. The 

 microdissection method has demonstrated that this sphere area is 

 liquid in contrast to the surrounding jellied cytoplasm. The pio- 

 neer observers of mitotic division, such as Auerbach, Hertwig, 

 Butschli and Fol, described the accumulation of a hyaline plasma 

 at the astral centers and suggested that the astral radiations are a 

 result of protoplasmic currents. Later investigators, such as Morgan, 

 Wilson and Conklin, considered this view as the most probable one. 



* The experiments, upon which this paper is based, were conducted in the 

 Research Division of Eli Lilly and Company, at the Marine Biological Labora- 

 tory, Woods Hole. The experiments constitute a part of a joint research project 

 in which Dr. G. H. A. Clowes and the writer are engaged. 



^Chambers, R. Microdissection studies. II. The cell aster: A reversible 

 gelation phenomenon, J. Exp. ZooL, 1917, xxiii, 483. 



'^Wilson, E. B., Experimental studies in cytology. I. A cytological study of 

 artificial parthenogenesis in sea-urchin eggs, Arch. Entwcklngsmechn., 1901, xii, 529. 



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