222 L. V. HEILBRUNN 



the strands are torn from their attachment and the shape of the 

 egg can remain spherical. 



The conception of astral radiations or gelatinous strands of 

 some kind attached to the periphery of the cell is of importance 

 in any theoretical interpretation of cell division. That there is 

 actually such an attachment is also indicated by a direct obser- 

 vation of the egg during the mitotic process. On a number of 

 occasions I have noticed that the first appearance of the amphi- 

 aster in the egg is followed by a change in the outline of the sur- 

 face contour. The hyaline membrane, at first perfectly smooth, 

 now appears slightly crenate. This crenate appearance is more 

 evident when the egg is looked at from one pole of the mitotic 

 spindle, and is apparently due to the pull of gelatinous strands 

 which radiate from the centrosphere. I have not been able to 

 observe such a crenate appearance in all eggs. 



INHIBITION OF SPINDLE FORMATION 



The measurements of cytoplasmic viscosity recorded in the 

 previous section afford evidence that the appearance of the 

 mitotic figure is closely bound up with gelation phenomena. 

 Much more convincing evidence can be obtained experimentally. 

 My earlier work showed that artificial stimulation to mitosis, 

 no matter what the reagent, always involves a preliminary gela- 

 tion of the cytoplasm. These observations indicated that there 

 is a definite causal sequence, but there was nothing to show that 

 gelation was more than a secondary phenomenon, having no 

 direct relation to the formation of the mitotic figure. In order 

 to show that the appearance of the spindle depends absolutely 

 on a preliminary cytoplasmic gelation, it is necessary to show that 

 suppression of the gelation in every case results in a suppression 

 of the spindle. This I have been able to do. 



In searching for an antigelatinizing agent, I was guided by 

 the earlier observations of Hertwig ('90) and Wilson ('01). The 

 former discovered that cold effectively prevented the appearance 

 of the amphiaster, the latter found that ether acted in a similar 

 manner. 



