Sonic Pheiiomena of Regeneration in Limnolrilus and relatod Fornis. 403 



Several facts of importance are to be gathered from these data. 

 Tu the first place it is sliown tliat so long as tlie intestine does not touch 

 tiie posterior end of the body wall no regeneration occurs from this 

 point. In onler to establisli witli inore certainty just how far this lack 

 of regeneration is diie to the absence of the intestine it is of primc 

 importance to determine the relation of the ventral nerve cord to the 

 (Hit end of the body wall. It has been found in the earthworm (Mor- 

 gan 02) that when the ventral nerve cord does not touch the cut sur- 

 face at the anterior end no regeneration takes place and therefore if 

 the nerve had been injured in the experiments being considered here 

 the absence of regeneration could be attributed to this fact. Sections 

 of 75 individuals showed that in every instance the nerve was present 

 at the cut surface. This then precludes the possibility of a lack of 

 j)roper nervous Stimulus. Another important question is that of proper 

 nourislinuMit. There can ])o no doubt that there was an ample blood 

 su])ply at the cut surface for, even when the Worms lived only a coni- 

 ]iaratively short time, blood vessels always ran down to the end of the 

 body; either the large dorsal blood vessel remained uninjured or eise 

 vessels quickly regenerated. All the tissues in the region of the wound 

 were bathed in a perfect flood of blood. As will be described later, 

 cell proliferation occured at the posterior end of the body wall during 

 the absence of the intestine. Therefore it was not starvation which 

 })revented regeneration. Neither could the lack of regeneration be due 

 to the level at which the worm was cut since in all cases in which the 

 intestine was absent the posterior end of the body was at a level from 

 which regeneration occurs under normal conditions and all further doubt 

 on this point is dispelled by the fact that the intestine frequently re- 

 generated and upon its touching the body wall growth proceeded in 

 the usual manner, even if as much as two or three weeks had elapsed 

 before the intestine came in contact with the posterior end of the body. 

 Controls showed that the piercing of the body wall with the needle 

 did not effect the result. It is true that many of the worms lived but 

 a weck and some objection might be raised on the ground that the 

 body wall would have regenerated if it had had sufficient time. But the 

 normal regeneration occurs in less than a week and in these experi- 

 ments, even those worms from which a piece of the intestine had been 

 removed could constrict ofi the empty somites and form at least an 

 anal somite within a week. Furthermore in quite a number of indi- 

 viduals the intestine was not present in the last segment for two weeks 

 and in other individuals for three or four weeks, a length of time which 



