CELL-DIVISION 



during the cleavage-cycle of the egg. It is the second, the 

 greater, which comes prior to the appearance of the cleav- 

 age-furrow, with which we are primarily concerned. 

 Secondly, during both periods the egg is spherical. The 

 change in form from spherical to ellipsoid occurs once only 

 during a cleavage-cycle; It marks the end of the period of 

 greater susceptibility. These two findings possess especial 

 significance for an interpretation. 



Table III. — The Rate at Which Eggs of Arbacia Disintegrate in Distilled 

 Water at Intervals after Insemination* 



* Eggs of Arbacia are inseminated, and at intervals after insemination 5 drops of them are mounted 

 under the microscope in 15 cc. of distilled water. The first column gives the number; the second, 

 the time after insemination; the third, the time to cytolysis; and the fourth, the stage of the egg at 

 the time of exposure. 



