GRAFTING AND REGENERATION 175 



the small piece was strikingly different from that of the major com- 

 ponent. The new head had the typical red-brown color of L. rnbelhis, 

 that forms a strong contrast to the grayish blue color of A. terrestrisl 

 The result shows that the color of the regenerated part has not been 

 influenced by that of the posterior component, and this is all the more 

 interesting, as Joest points out, because the small piece that was left 

 after the worms pulled apart was too small to have lived independently 

 for any length of time, and must have derived all its nourishment 

 from the larger piece. 



In other experiments pieces of one species were cut from the side 

 of the body and grafted upon the cut-surface of the anterior end (or 

 elsewhere) of another species. In one of these experiments a piece 

 from the side of A. terrestris, that extended over five or six segments, 

 was sewed upon the anterior cut-surface of L. rubellus (from which 

 the anterior five segments had been removed). In about a month new 

 tissue appeared on the ventral side between the two pieces, and a 

 little later a complete head developed, whose dorsal side was made up 

 of the small piece (Fig. 53, C). The grafted piece was dark, and the 

 new, regenerated part light in color and continuous with the brown 

 color of L. rubellus, from which the new part had arisen. It is 

 important to notice that the four segments of the graft are completed 

 by four segments of the new part. After three months the new part 

 had assumed the red-brown color of L. rnbellns. The color of the 

 grafted piece had not changed. We see in this case that even the 

 presence of a part of another worm in a regenerating region does not 

 have any influence, at least so far as color is concerned, on the new 

 part, even though its segments supplement some of those of the 

 new part. The new tissue seems to have come entirely from the 

 major component, and to have carried over the color characteristics 

 of the old part. 



It has been shown that when two posterior pieces are united by 

 their anterior ends the combination must sooner or later die, since it 

 has no way of procuring food. The question arises : What will hap- 

 pen if one of the two components is cut in two near the place of 

 union ? Will a head then develop on the exposed aboral surface, 

 because a head is needed to adapt the worm to its surroundings, or 

 possibly, if it occurred, because the major component exerts some 

 sort of influence on the short, attached piece, as happens in hydra 

 and in tubularia? Both Joest and I carried out an experiment 

 of this sort, and found that a tail and not a head regenerated, as 

 shown in Fig. 16, F. The experiment is, however, insufficient to 

 answer the question, since the region in which the second cut was 

 made is a region from which only a tail (and not a head) arises, even 



1 The prostomium was misshapen, so that its specific character could not be made out. 



