CELL DIVISION — SPINDLE IN SEA-URCHIN EGGS 223 



In the course of my work I have been able to discover a large 

 number of substances which prevent the normal gelation of the 

 egg or reverse it after it has occurred. 



If the fertilized eggs are treated with antigelatinizing agents 

 before the spindle has appeared, spindle formation is inhibited and 

 cell division does not occur. This suppression of cell division 

 need not involve injury to the egg, and in most cases when 

 the eggs are returned to normal sea-water they resume their 

 development. 



The following substances were found, in proper concentration, 

 to prevent gelation: ether, chloroform, acetone, paraldehyde, 

 propyl alcohol, isoamyl alcohol, ethyl butyrate, ethyl nitrate, 

 acetonitrile, nitrbmethane, chloral hydrate, phenyl and ethyl 

 urethanes. 



In studying the effect of these substances on the egg, the usual 

 procedure was as follows: Soon after fertilization, eggs were 

 placed in a series of concentrations of the desired reagent. Usu- 

 ally about six different concentrations were employed, and they 

 were kept in tightly stoppered vials. Then, as soon as possible, 

 the cytoplasmic viscosity of the eggs was tested. As my studies 

 progressed, I was able to predict the fate of the various groups 

 of eggs. A certain degree of antigelatinizing action always pre- 

 vented the formation of the spindle. The weaker solutions, un- 

 able to produce the requisite effect on cytoplasmic viscosity, did 

 not prevent the division of the cell. On the other hand, too con- 

 centrated solutions produced intense gelation and killed the eggs. 

 Intermediate concentrations gave the desired results. In these 

 cytoplasmic gelation was inhibited or reversed, and viscosity de- 

 terminations showed the cytoplasm to have a liquid consistency. 

 In such eggs with fluid cytoplasm, no mitotic figure ever formed. 

 Nevertheless, the eggs were not all killed by the reagent, as some 

 were able to resume their development on return to sea-water. 



The results obtained with the fourteen substances enumerated 

 above were all similar. Individual differences occurred, but in 

 every case the general scheme was the same. It will scarcely be 

 necessary, therefore, to record all of the experiments, and I 

 shall content myself with presenting only some representative 



