576 bulletin: museum of comparative zoology. 



compaied with the stomodea in controls), its position (in regenerated 

 tissue with its axis pointing toward the nerve ring formed by the 

 connectives, brain, and nerve cord), and by the complete absence of 

 evidence that it was produced by muscular contractions. The re- 

 generated brain (cb.) was joined with the ventral nerve cord by 

 abnormally short connectives. 



There was some doubt in the preceding cases whether the cut which 

 removed the brain and the three anterior segments, also removed 

 the end of the nerve cord and the bases of the connectives. This 

 doubt was suggested by the fact that in some of these cases the hyahne 

 nerve sheath passed around the end of the nerve cord, as normally, 

 while in the other cases the absence of the sheath could not be demon- 

 strated. But in number 272 the sheath (Fig. 4, lent, hyl.) clearly 

 terminates a considerable distance back of the bases of the connectives. 

 It is conceivable, of course, that the anterior part of the old sheath 

 had degenerated, but I found no evidence of it. It is therefore 

 probable that the regenerating end of the nerve cord bifurcated to 

 form the connectives and did so without being stimulated by contact 

 with the digestive tube. 



These six cases clearly demonstrate that the regeneration of the 

 connectives, of the brain and its two main nerves, of the stomodeum, 

 and of the segmented muscular body wall, can proceed in the absence 

 of any stimuli depending upon the close proximity of the digestive 

 tube. 



2. Second Group of Experiments. 



The observations of Goldfarb show that regeneration in the earth- 

 worm ('09) and the annelid Amphinoma pacifica ('14) was not con- 

 tingent upon contact with, or stimulation from, the nerve cord or 

 central nervous system. These observations, in connection with 

 those described above, suggested the possibility that if both the nerve 

 cord and the digestive tube were excised, head structures might 

 regenerate before either tube or cord had grown forward to the an- 

 terior end. The operation described in the first group of experiments 

 was repeated on one hundred and three individuals of Eisenia foctida, 

 and, in addition, in each of these worms the nerve cord was removed 

 from the first five or six segments back of the plane in which the body 

 was transected. 



Sixty-nine individuals survived the operation. I found no cases 

 in which head structures had regenerated before the nerve cord and 



