Grafting of Tuhularia 



345 



of regeneration than contact with the major component. The 

 only cases where it seems to me we are justified in looking for the 

 influence of one upon the other is where the hydranth is developed 

 partly in the long piece and partly in the short one. This did not 

 take place in any of the experiments. 



5 THE INFLUENCE OF THE CURRENTS ON REGENERATION AFTER 



GRAFTING 



Experiment I. Two short pieces grafted in the same direction. 

 It was suggested to me by Professor Morgan, that the current in 

 the two pieces of which a graft is composed, may have something 

 to do with the order of regeneration in the outer ends of grafts. 

 Soon after a piece is cut from the stem of Tuhularia, the wound 

 closes, and rapid circulation begins. The current is easily seen 

 coursing up one side of the piece and down the other. When two 

 pieces are united the currents do not always flow from one piece 

 into the other. Instead, the current may be seen flowing up one 

 piece and turning at the line of union as if stopped by a membrane, 

 and continuing down the other side. Frequently, however, the 

 current continues to flow up one side and on into the other piece. 

 In Fig. 19 (-E and F) these two cases are shown. In E the current 

 is continuous; in F it is separate in the two pieces. 



Fig. 19 



Small pieces, measuring 1.5 to 2 mm. in length, were cut from 

 diff'erent stems from a region at least i cm. back of the hydranth. 

 One piece was inserted in the other so that the oral end of one 

 overlapped the aboral end of the other (Fig. 19, A). At the end of 

 twenty-four hours each graft was carefully examined under suffi- 

 cient magnification to detect the direction of the currents. All of 

 the grafts in which the circulation was continuous from one com- 

 ponent to the other (Fig. 19, E) were put in lot A, while those in 



