SoiiH' Plu-niimcna ol ItcL'fiuMalioii in l.iiniiodiilus and related Foi'ins. 105 



being niade for tlic addition of iicw lissuc wliicli ])roco.ss, wIhmi once 

 it is begun, i)rc grosses rajiidly. 



Provid(>J an iiulividiial livcd a sufficieut leiigth of tinie the intes- 

 tina usually regenerated biil in tlif fxjx'rinients already described 

 foui' iiidividnals sliowed no indic-ations of new tissue in the intestinc 

 i'veii afteras niuch as four weeks had elapsed (See series 6 and 7 p. 400). 

 The fact that in each of these cases the intestine was cut off at the lOth 

 >omite and did not regenerate is vejy significant. All of these cases 

 occured in Tuhifex and it is well known that in general posterior, regene- 

 ration does not take place in a head piece of Tuhifex unless it possesses 

 at least ten somites. As a matter of fact in this series there is one 

 individnal in which the intestine was in contact with the posterior 

 end of the body at the lOtli somite and yet no outgrowth appeared 

 i'ven after several weeks. Therefore it is safe to conclude that what- 

 ever cause prevents the growtli of the entire body from this level iike- 

 wise prevents the intestine frotn regenerating. 



B. Anterior End. 



Attempts at drawing out the intestine from the anterior end of 

 Limnodrilus and Tuhifex within levels at which anterior regeneration 

 norinally occurs proved unsuccessful because the small diameter of 

 ilie biuly in this region tnade the insertion of the forceps rather diffi- 

 cult without injuring the somites to such an extent as to cause them 

 to constrict off. However at levels posterior to a poInt at which an- 

 terior regeneration of the body takes place the diameter of the body is 

 greater, and in this region the intestine was reraoved from the anterior 

 end of pieces in order to learn whether or not the intestine would 

 regenerate where regeneration of the body as a whole does not occiir. It 

 will l)e remembered that the intestine does not regenerate from the 

 posterior end of a piece anterior to a point at which the body as a whole 

 does not regenerate posteriorly. The intestine was removed from several 

 somites at the anterior end of pieces in the neighborhood of the 20th 

 somite. Usually most of the intestineless somites would constrict off 

 but some individuals were obtained in which one or two intestineless 

 somites remained attached. In none of these did the intestine re- 

 generate more than to close the cut end. The body wall healed but 

 as one would expect no regeneration occured. 



Since it was not possible to remove the intestine from the anterior 

 end of Limnodrilus or Tuhifex at levels from which anterior regene- 

 ration of the l)üdy occurs Lumhricus herculeus was used for this purpose, 



