PHYSIOLOGY OF CELL-DIVISION 



377 



TABLE 1 



After three hours in sea-water of 62.5 per cent dilution the majority of fer- 

 tilized eggs were still uncytolyzed, though greatly distended; at 65 per cent about 

 half were cytolyzed and depigmented, the remainder swollen but intact. 



then rapidly declines, and at the time of appearance of the 

 furrow the membrane is only slightly extensible; at this time 

 many eggs undergo cytolysis in dilutions so low as 40 or 42.5 

 per cent, and in a dilution of 60 per cent all are rapidly and com- 

 pletely cytolyzed, the majority within two or three minutes. 

 This state of low resistance persists during the three or four 

 minutes occupied by the formation and extension of the cleavage- 

 fuiTow; after the latter is complete the former resistance quickly 

 returns. At ten minutes after cleavage the resistance is found 

 to be practically the same as at ten minutes before cleavage. 

 Thus during the period of fifteen or twenty minutes occu- 

 pied by the processes, preparatory and active, of cytoplasmic 

 division, the membrane undergoes a reversible change of state 

 which profoundly affects its extensibility and coherence, and 

 presumably its permeabihty and other general properties. A 

 similar change is found at the second and third cleavage, and 

 probably occurs at all cell-divisions (see table 2). 



In the following table the results of a typical experiment 

 are described in detail. 



It is clear from these results that the eggs very readily under- 

 go cytolysis at the time when the cell-body is di\dding, and 

 become again resistant in the intervals between divisions. These 

 observations were not carried beyond the third cleavage, be- 

 cause of increasing variation in the state of different eggs, and 



