Simic Plimoiiicna of Regenoralion in l.ininodrihis and idatcd Forn;s. 300 



eilt in two at tlie region of greatest diameter i.e. betweon tlie lOth 

 and tlie 20t h soniites, usually aboiit the lüth. The worms had becn 

 previously anaesthetized to insiire their remaining perfectly motionless. 

 The hoad piece was held by piercing its body wall, but not the intes- 

 tino, with a noodle near the posterior end while the tip of the foreceps 

 was inscrted into the open posterior end, the intestine seized and drawn 

 out a sliort distance and cut off. The Operation was performed with 

 the aid ot a binocular microscope. It was found that the more com- 

 pletely the worms were anaesthetized the more easily could the intes- 

 tine be drawn out. The Operation was rather drastic and at first the 

 mortality was high but as skill was gained the death rate became 

 greatly less until frequently nearly all the individuals lived provided 

 no infection took place. The amount of intestine that could be re- 

 moved varied, froni one-foürth or one-half of a somite to as much as 

 three somites. Of course the intestineless somites were frequently 

 coiistricted off but if an Operation had been well performed they were 

 less liable to do so. The results of several series of Operations follow. 



Ist Series — Apr. 24th 08, Limnodrilus. — Seven individuals were 

 fut in two between the llth and the 16th somites and a varying amount 

 of intestine removed. At the end of a week two were alive and showed 

 no signs of regeneration, one having lost one half segment and the 

 other two segments of intestine. The first individual died shortly- 

 after this but the second lived three weeks. However the empty so- 

 mites soon became infected and dropped off. 



2nd Series — Apr. 28th 08, Limnodrilus. — Ten individuals were 

 lut at the 16th somite and about one segment of intestine removed. 

 Three lived a week and showed no signs of regenerating the body wall. 

 At the end of two weeks one was still alive but the intestineless so- 

 mites had been constricted off so that the intestine touched the end 

 of the body which had then begun to regenerate. 



Several other Operations were performed with similar results, none 

 of the Worms living very long. Nothing Avas done during the Summer. 

 In the Fall, at Princeton, Limnodrilus of the proper size could not be 

 ' »btained but some very large specimens of Tuhifex were to be had and, 

 consequently, thereafter this form was used entirely. The removal 

 of the intestine seemed to be more easily accomplished in Tuhifex 

 than in Limnodrilus. 



3rd Series — Nov. 28th 08. About one segment of intestine was 

 removed between the 13th and the loth somite of ten individuals. 

 At the end of a week four showed no signs of regeneration and the 



Zeitschrift J. wissensch. Zoologie. XCV. Bd. 26 



