CELL DIVISION — SPINDLE IN SEA-URCHIN EGGS 225 



July 10th. Eggs fertilized at 10:16 a.m. were placed in a 0.13 per 

 cent solution of chloroform at 10:26| a.m. At 10:33 a.m. normal fer- 

 tilized eggs and some of those in the chloroform solution were centri- 

 fuged simultaneously, the handle being turned 50 times in 29 seconds. 

 The normal eggs had a hyaline zone barely indicated, whereas the chlo- 

 roformed eggs showed a h3^aline zone extending halfway along the axis 

 of stratification. The eggs treated with chloroform did not segment. 



Various experiments with paraldehyde showed that a 4 per 

 cent solution was very effective in reversing gelation. 



July 10th. Eggs fertilized at 11:51 a.m. were transferred to 4 per 

 cent paraldehyde at 12:02 p.m. At 12:09 p.m. normal eggs and those 

 exposed to paraldehyde were centrifuged simultaneously. In the nor- 

 mal eggs the hj^aline zone was barely indicated, in the treated eggs it 

 extended through half of the egg. The concentration of paraldehyde 

 used was sufficient to prevent segmentation. 



The following experiments deal with the effects of various 

 other substances which act like ether and chloroform. 



July 17th. Chloral hydrate. At 12:05| to 12:06 p.m., eggs fertilized 

 24 minutes previously (at 11:42 a.m.) were subjected to seven different 

 concentrations of chloral hydrate, varying from gV P^i" cent to 1 per 

 cent. Of these concentrations, 1 per cent of the reagent produced 

 coagulation, but concentrations of \ per cent to y^2 P^i' cent had the 

 opposite effect and produced reversal of the normal gelation. These 

 concentrations prevent segmentation, but the inhibition is only tem- 

 porary, and the eggs segment (although often somewhat irregularly) 

 upon return to sea-water. 



In the above description many of the less important details of 

 of the experiment were omitted. The following experiment is re- 

 ported more fully: 



July 22nd. Amyl alcohol. At 11:44 a.m., eggs fertilized five min- 

 utes previously were put into vials containing various concentrations 

 of isoamyl alcohol (isobutyl carbinol). Six vials were used. A con- 

 tained 2 per cent of the alcohol, B 1.33 percent, C 1 per cent, D 0.67 per 

 cent, E 0.33 per cent, and F 0.17 per cent. 



At 11:51 A.M., eggs in A and normal eggs were centrifuged simul- 

 taneously, the handle of the centrifuge being turned 50 times in 29 sec- 

 onds. The A eggs were evidently coagulated, for they showed no strat- 

 ification; the normal eggs had the hyaline zone barely indicated. At 

 12:02| P.M., eggs in B and normal eggs were centrifuged simultaneously 

 at the same speed as in the previous test. They, too, gave no evidence 

 of stratification. At 12:12| p.m., the eggs in D and normal eggs were 



