CELL DIVISION — SPINDLE IN SEA-URCHIN EGGS 235 



June 29th. At 11:38 a.m., some unfertilized eggs were dropped into 

 distilled water, and one minute later they were transferred out of the 

 distilled water into A, which contained pure sea-water, and B, which 

 contained 2^ per cent ether in sea-water. 



At 11:50, the eggs in A and B were centrifuged simultaneously, the 

 handle being turned 50 times in 30 seconds. When the centrifuged 

 eggs from A and B were compared, both lots appeared the same. In 

 both cases most of the eggs showed stratification, with a wide and dis- 

 tinct hyaline zone. In both cases, a considerable number of the eggs 

 were cyiolyzed and showed not a trace of stratification. 



If the normal gelation is due to an abstraction of water, then 

 it should be possible to show an antagonism between cold and 

 hypertonic solutions, whch would be comparable to the effect of 

 cold on the normal gelation. So far, my results in this direction 

 have not been completely successful. Although I have been 

 able to show that cold retards the gelatinizing effect of hyper- 

 tonic solutions on the unfertilized egg, I have not yet demon- 

 strated that cold can cause a reversal of gelation when once this 

 has been produced by hypertonic solutions. But only a single 

 experiment has been tried, and perhaps further observation will 

 also show this to be true. The following experiments shows that 

 cold tends to prevent gelation of the cytoplasm by a hypertonic 

 salt solution: 



August 30th. A hypertonic solution was prepared by adding 8 cc. 

 of 2| n NaCl to 50 cc. of sea-water. This solution was then divided 

 into two portions, of which A remained at room temperature, and B 

 was kept at a temperature which varied from — 1.3° to +1°. At 10:58 

 A.M., unfertilized eggs were placed in A. At 11:08 a.m., some of the 

 eggs in A were removed to B. At 12:31 p.m., eggs in A and B were cen- 

 trifuged simultaneously, the handle being turned 50 times in 30 seconds. 

 The eggs in B showed a gray cap and a hyaline zone eivtending about 

 one-third of the distance along the axis of stratification. The eggs in 

 A showed not a trace of stratification. 



If the gelation which occurs normally is due to water abstrac- 

 tion, it might be also expected that when the egg is made to take 

 up water, this gelation could be reversed. This is in fact true, 

 and hypotonic solutions effectually cause a reversal of gelation 

 in the fertilized egg. This was shown clearly by centrifuge tests. 

 Because of this antigelatinizing effect, hypotonic solutions act 

 like ether and prevent segmentation without otherwise injuring 

 the egg. 



