410 



lost approximately 25 segments which have been replaced (?) by 35 new 

 ones. The new part is drawn to larger scale in Fig. 8 as seen from 

 above. The slit like terminal opening is clearly shown in Fig. 9. 

 Sections of this worm show a ventral cord extending to the end of the 

 new part. There is no brain present. 



Finally I have examined sections of another worm (Oct. '98 — 

 Jan. '99) that also shows no brain, and the ventral cord extends to 

 the end of the new part. 



These results show that the newly regenerated part is, in those 

 cases where many segments are formed, a tail and there is produced 

 a worm with two tails turned in opposite directions. 



Heretofore I had assumed the new part to be a head incompletely 

 developed and had imagined that had the experiment lasted longer a 

 head would develop at the anterior end. Sections show however that 

 there is no brain and that the ventral cord extends into the last 

 (youngest) segments of the new part. It may still, perhaps, be ob- 

 jected that my evidence is incomplete since such parts might sub- 

 sequently develop a brain at the distal end. Fortunately I am able 

 to anticipate and refute any such objection. It is well known that the 

 nephridia of the earthworm open internally by nephrostomes that lie 

 in the segment in front of that containing the greater part of the 

 nephridial tube. If the new part be in reality a tail the nephrostomes 

 of its nephridia should be turned backwards, i. e., towards the old tail 

 and the main part of the nephridial tube should lie in the segment 

 distal to the one containing the nephrostome. On the other hand if 

 the new part be an incompleted head end then the nephrostomes should 

 be turned in the same direction as are those in the old part, i. e. 

 forward and the nephridial tube should lie in the next segment behind 

 the one containing the nephrostome. 



The serial sections of all these worms that have de- 

 veloped many new segments show in the clearest manner 

 that the nephrostomes in the new part are turned back- 

 wards, i. e., towards the old part, and the main part of 

 the nephridial tube lies in the segment distal to the 

 one containing the nephrostome. This arrangement 

 shows beyond question that the new part is a tail and 

 not a h ead end. 



Bryn Mawr College, Bryn Mawr, Penn. U.S.A. 

 Jan. 26, 1899. 



