BEGINNINGS OF CO-OPERATION 73 



A few eggs from the larger mass spilled over into 

 this strait. The whole slide was placed in a moist 

 chamber to avoid drying, and examined from time 

 to time. In a trifle over fifty-five minutes half the 

 eggs in the densest drop had passed first cleavage. A 

 half-minute later, 50 per cent of those in the strait 

 were cleaved, and twenty seconds later half of the 

 more isolated ones had divided. The time to 50 per 

 cent second cleavage ranged between eighty-four 

 minutes for the crowded eggs and over eighty-six 

 and a half minutes for the isolated ones. 



This was repeated with four thousand eggs or 

 thereabouts in the denser population, almost six 

 hundred of which spilled through and formed a flat 

 apron over the bottom of the second drop, in which 

 there were thirteen other eggs scattered singly about 

 the relatively unoccupied space. Under these condi- 

 tions the time to 50 per cent first cleavage was ap- 

 proximately fifty-two, fifty-eight and sixty minutes 

 respectively, and the difference at the middle of the 

 second cleavage was even greater. 



In association with Dr. Gertrude Evans, who is a 

 good, skeptical research worker, this experiment was 

 repeated in many different ways; and there remains 

 in my mind no doubt but that under a variety of 

 conditions the denser clusters of these Arhacia eggs 



