398 F. H. Krecker, 



beeil cut in two seven days previous to this and the absence of re- 

 generation seemed unusual, especially in view of the fact that other 

 individuals operated upon at the same time had formed considerable 

 new tissue. The condition of the worm was carefully noted and the 

 •animal was then kept a week longer after which time it was again 

 examined. There had been practically no change; there was no re- 

 generation of the body wall and the intestine ended free in the coeloin. 

 The fact that the body wall had not regenerated was extremely strik- 

 ing and suggestive. The thought occured that there might be a corre- 

 lation between the intestine and the body wall; in other words that 

 regeneration failed to oceur because the intestine did not touch the 

 body wall. 



Upon referring to the literature it was found that some results 

 obtained by Haeper (04) from work on SUjlaria lacustris indicated 

 that at least certain parts of the body do not regenerate when the 

 alimentary tract is not injured. Harper found on removing a corner 

 of the head somite including the prostomium without injury to the 

 pharynx that the ectoderm would close over the wound but that no 

 regeneration took place. To test this point for Limnodrilus and Lum- 

 hriculus the prostomium was removed from several individuals but 

 by the end of a week it had regenerated in all. From observations 

 on Planaria maculata Bardeen (Ol) concluded that the nutritive 

 currents sent out by the intestine have much to do with the formation 

 of »embryonic tissue«. Morgan (Ol) removed a portion of the body 

 wall from the ventral surface of the earthworm so as to expose an ante- 

 rior end of the ventral nerve cord and in such cases he obtained a head- 

 like outgrowth in which there was frequently no alimentary tract. 

 Therefore he maintained that the presence of the intestine is unneces- 

 sary for the regeneration of a head. 



In view of what had occured in the individuals already mentioned 

 it seemed important to determine what relation, if any, the ab- 

 sence of the intestine has to the regeneration of the worm. In order 

 to do this it was necessary to prevent the intestine from touching the 

 cut surface of the body wall and the only way in which this might be 

 accomplished seemed to be by taking out a bit of the intestine. Va- 

 rious methods were attempted unsuccessfuUy until the following was 

 tried which was, indeed, the simplest. A finely pointed pair of forceps 

 was ground down to a still finer point, care being taken that the tips 

 met perfectly. A needle was also sharpened that it might cause as 

 little injury as possible. Then worms of the largest diameter were 



