164 



REGENERATION 



by Rand. A part of one hydra is grafted upon the side of another 

 one in the following way. A groove is scratched in a film of soft 

 paraffine covering the bottom of a dish filled with water. Another 

 groove is made at right angles to the first one, and opening into it. 

 A hydra (the stock) is placed in the first groove, and a wound made 

 in its side with a knife. Another hydra is cut in two, and one piece 

 (the graft) placed in the other groove, and its cut-surface brought 

 into contact with the wound in the side of the first individual. If 

 the operation is successful the exposed surfaces of the two hydras 



B 



FIG. 48. After Rand. A. Head of Hydra cut off. After eight days. A 1 . Same after thirteen 

 days. Three tentacles misplaced. A 2 . Same after eighteen days. A 8 . Same after twenty- 

 one days. Misplaced tentacles absorbed. B. Anterior end of Hydra fusca, grafted upon 

 side of body of another individual. Half an hour after operation, /fl. Same after four days. 

 B 1 . Same after thirty-eight days. fi. Same, foot-region after forty-nine days. B*. Same 

 after separating. Fifty-second day. 



quickly unite, and the combination may be taken out of the groove. 

 If the piece grafted on the stock included about the anterior half 

 of a hydra, a two-headed animal results, as shown in Fig. 48, B. 

 Although the graft has been united to the side of the stock, it soon 

 assumes an apparently terminal position (Fig. 48, B 1 }. This is due 

 to the graft sharing with the anterior end of the stock the common 

 basal portion of the stock. A slow process of separation of the two 

 anterior ends now begins, brought about by a deepening of the angle 

 between the halves (Fig. 48, 2? 2 ). This leads ultimately to a com- 



