498 ROBERT CHAMBERS, JR. 



III. DISCUSSION 



The pioneer observers of mitotic division, for example, Auer- 

 bach, O. Hertwig, Biitschli and Fol, described the accumula- 

 tion of hyaline plasma at the astral centers and suggested that 

 the astral radiations are a result of protoplasmic currents. Later 

 investigators, such as, Rhumbler ('96, '99), Morgan ('00), Wilson 

 ('01) and Conklin ('02), were convinced that centripetal currents 

 do occur in the formation of the aster. Experimental evidence 

 described in this paper confirms these views. It is necessary, 

 however, to make a distinction between the general hyaloplasm 

 and the substance constituting the astral rays and sphere. The 

 formation of the aster consists in the gelation of the hyaloplasm 

 which comes under the influence of the astral center. A hyaline 

 liquid separates out during the gelation and flows in innumerable 

 centripetal paths toward the center where it accumulates to 

 form the sphere. This centripetal flow brings about an arrange- 

 ment of the gelled hyaloplasm containing the cell-granules into 

 radial strands separated by the hyaline liquid paths. This 

 produces the astral figure. The strands of gelatinized cytoplasm 

 merge peripherally into the surrounding liquid cytoplasm or 

 reach and anchor themselves in the substance of the gelled egg 

 surface when the aster is fully formed. The liquid rays merge 

 centrally into the substance of the sphere, the liquid of the rays 

 and of the sphere being thus identical. 



The term ray could be applied to the gelled strands as well as 

 to the liquid paths. However, the liquid paths are tributaries 

 of the central sphere of the aster and it appears very likely 

 that they condition the radiate appearance of the gelled cyto- 

 plasm. It seems appropriate, therefore, to limit the use of the 

 specific term ray to the centripetal paths as I have done in this 

 paper. 



At a meeting of the American Society of Zoologists in Decem- 

 ber, 1916, before which this paper was read, Heilbrunn ('17)^ 

 presented results of investigations on cell division which make 



' Heilbrunn's paper giving his results in detail will appear with this paper, 

 or shortly after. 



