230 L. V. HEILBRUNN 



At 11:17 A.M., eggs from C were centrifuged simultaneously with a 

 control lot of untreated fertilized eggs, the handle being turned 50 

 times in 29 seconds. Whereas the normal eggs had the hyaline zone 

 well indicated, the eggs from C showed not a trace of stratification. 



At 11:25^ A.M., eggs from B were compared with normal control 

 eggs. The centrifuge handle was turned 50 times in 29 seconds. The 

 normal eggs showed a hyaline zone extending a third of the distance 

 along the axis of stratification. The B eggs showed not a trace of a 

 hyaline zone. 



At 11:36^ A.M., eggs from A were compared with normal eggs. The 

 centrifuge handle was turned 50 times in 28 seconds. The normal 

 eggs showed a prominent hyaline zone, extending at least a third of the 

 distance along the axis of stratification. In the A eggs, the hyaline 

 zone was barely indicated. 



At 11:53 A.M., the eggs from D and from E were centrifuged, the 

 handle being turned 50 times in 30 seconds. Neither eggs from D nor 

 those from E showed any trace of stratification. 



Thus it is evident that the addition of hy pertonic NaCl to sea-water, 

 has the effect of intensifying the gelation of the egg cytoplasm. 



At 12 M, the control of untreated fertilized eggs contained eggs in 

 the two-celled stage, but there was no segmentation va. A, B, C, D, 

 E. At 2 P.M., these dishes were again examined. At this time cleavage 

 was occurring in A. In B there was nuclear division without cytoplas- 

 mic division. In C, D, and E there was neither nuclear nor cytoplasmic 

 division. 



At 2:24 P.M., eggs from B and from C were centrifuged, the handle 

 being turned 50 times in 28 seconds. In the C eggs the hj^aline zone 

 was indicated in some eggs, but not very clearly. In the B eggs the 

 hyaline zone was prominent, extending through about one-third of the 

 egg. But it was not very transparent, for a cortical zone of granules 

 covered it. This indicates a cortical gelation. It will be remembered 

 that the B eggs are those in which nuclear division without cytoplasmic 

 division Avas found to take place. 



The effect of potassium cyanide is worth recording. Even in 

 very dilute concentrations, the cyanide inhibits cell division. 

 But, curiously enough, the early phases of mitosis are able to 

 continue in such concentrations. Likewise, the final stages of 

 the process can go on. The explanation that I would offer is a 

 very simple one. Potassium cyanide intensifies gelation and the 

 normal gelation is rendered irreversible. This can be shown true 

 by viscosity measurements.^ 



1 Moreover, it is directly in line with my previous observation that cyanide 

 prevents swelling of the gel which forms the vitelline membrane of the egg. 



