Soino Phenomi'iia of Repcnoratiori in LimiiiHlrilus aiid related Forms. 4:07 



does not arise de novo froni the cctodcrni and tliat therefore in those 

 cases in which Morgan found a digestive tract it was very probabl/ due 

 to an outgrowth froni the old digestive tract. In the first series where 

 the nerve did not reach the anterior end there was no regeneration and 

 sincc wliere some regeneration occured the nerve was present it can be 

 assumed that some infhience is exerted by the nerve. Although, as 

 we have seen, regeneration does occur without the presence of the 

 digestive tract neverthek^ss ander these circumstances, as the control 

 in series two shows, the new growth is neither so extensive nor so per- 

 fect as that which is normally formed. This is evident both in the 

 length of the regenerated portion and in its segmentation. The latter 

 is distinctly shown in the normal groA\i:h, but in the abnormal type 

 the segmentation is not so clear, thougli there are some slight inden- 

 tations of the surface which might be looked upon as segmental depres- 

 sions. Internally the segmentation is still moro indistinct, in fact the 

 sections showed no signs of it. 



II. Internal Phenomena. 



The gi'osser processos in the regeneration of either the body wall 

 or the intestine can be followed with ease by external Observation but 

 the more minute changes, wliicli in the last analysis are no doubt of 

 great significance in the Interpretation of the phenomena of regene- 

 ration, can be traced only by means of sections. In the cases just con- 

 sidered, where there has been no regeneration in the absence of the 

 intestine, we have indications that the internal phenomena are radi- 

 oally different from those that are found under normal conditions 

 and, indeed, a histological examination of individuals from which the 

 intestine has been removed revealed certain remarkable and suggestive 

 variations from the normal course of events. These will be described 

 with some detail in the following pages. The account will deal chiefly 

 with those worms which have lost a part of the intestine. 



A. Posterior End. 

 The Closure of the Wound and the Strand. 

 The closure of the wound does not differ essentially from the 

 usual method. As soon as the body is severed the sharp contraction 

 of the muscles draws the edges of the wound together and closes the 

 aperture. The almost immediate Insertion of the foreceps to size the 

 intestine delays this process but does not prevent its completion once 

 the obstructions are removed. Tlie drawing out of the intestine causes 



