500 - ROBERT CHAMBERS, JR. 



the cytoplasm. The aster rays appear to be the channels in 

 which the centripetal flow occurs. 



3. The cytoplasm between the rays is in the gel state to which 

 the rigidity of the aster is due. The gel state is most pro- 

 nounced near the sphere and peripherally passes gradually into 

 the sol state of the cytoplasm lying beyond the confines of the 

 aster. When the aster reaches the periphery of the cell the 

 entire cell is rendered comparatively rigid. 



4. In the maturation figures of the egg nucleus the peripheral 

 aster forms a continuous gel with the surface layer of the egg to 

 which the figure is thus firmly attached. The confines of the 

 central aster pass insensibly into the surrounding liquid cyto- 

 plasm. 



5. A periodic reversal of the sol to the gel state and vice versa 

 has been demonstrated in the cell protoplasm during division. 

 The steps taken may be divided into the following series: (a) 

 When the aster is fully formed the greater part of the cell is a 

 gel. (b) The cytoplasm reverses to a sol state and the astral 

 radiations fade out while the sphere liquid collects at the two 

 poles of the nucleus, (c) The formation of radiations about the 

 spheres at each pole of the nucleus producing the amphiaster is 

 accompanied by a return to the gel state, (d) A return to the 

 sol state takes place in the equator of the cell. The nuclear 

 spindle now divides, a constriction around the middle of the cell 

 then follows and continues until the cell is cut in two. 



6. As a general rule, one may say that the reversal of the gel 

 to the sol state starts in the equator of the cell and spreads to the 

 poles. On the other hand, the reversal of the sol to the gel 

 state commences about the sphere and spreads peripherad. 



7. The gel state in living protoplasm is not inert. Even to 

 the eye, there is always a constant but very gradual change 

 among the granules embedded in the cytoplasmic gel. 



8. There are appreciable differences in the liquid state of the 

 cytoplasm in certain regions and at various times, e.g., the inte- 

 rior cytoplasm of the unfertilized and fertilized egg before the 

 aster is formed is slightly viscous, whereas, the contents of the 



