26 WM. A. KEPNER AND B. D. REYNOLDS. 



at which each event took place was made. At n : 38 A.M., June 

 10, 1920, a small fragment, c, Fig. 2, was cut off from a Difflugia 

 spiralis. The animal immediately withdrew its extended pseudo- 

 pods, but not completely within its shell. It then sent out two 

 new pseudopods, and at 11 : 39 A.M. the ends of both these were 

 cut off, a and b. The animal was so stimulated by this second 

 operation that it quickly retracted its pseudopods, and in doing so 

 was turned through an angle of ninety degrees, so that now its 

 mouth lay directed at right angles to the fragments, which were 

 lined up in a row. In a short time the animal extended a short 

 pseudopod which curved around alongside the neck of its shell and 

 fused with a at 11:40^ A.M. The cell-body was then moved 

 600 micra away and placed so that the side of its shell was toward 

 the remaining two fragments which had been left in their original 

 positions. By 11 :45 A.M. it had advanced again and fused with 

 fragment c. The animal was then stimulated with a glass rod, so 

 that it withdrew into its shell again; but by 11 :45^4 A.M. it had 

 sent out another pseudopod which fused with fragment b. Thus 

 within seven and three quarter minutes from the time the first 

 fragment was cut off the animal had picked up and reappropriated 

 all three fragments, though during the interval it had been stimu- 

 lated by the observer so violently as to make it contract four times, 

 and at one time it was moved six times its shell's diameter away, 

 through which distance it had to travel in order to get back to its 

 missing parts. 



It has not been determined exactly what the maximum range of 

 positive response is — i.e., the limit within which fusion always 

 occurs. One positive case was observed in which the cell-body 

 and fragment were separated by one and one half millimeters. 

 But chance wandering might have brought the animal within the 

 positive range. Be this as it may, chance can hardly explain the 

 large percentage of positive observations made. When the two 

 elements were separated by great distances, we encountered a 

 small percentage of negative reactions. However, in every case 

 which we observed where the cell-body and fragment were sep- 

 arated by a distance of 500 micra or less fusion always took place, 

 unless the cell-body was injured. It seems, then, that reunion is 



