409 



Sagittal sections were made through this worm. They show that the 

 ventral nerve cord extends into the new part to the very end, where 

 it abuts against the body-wall. If the new part were an anterior end 

 we should expect to find the ventral nerve cord terminating a few 

 segments before the end of the body and then extending around the 

 digestive tract as a pair of commissures to the brain — but this is 

 not the case and there is no brain on the dorsal side. The largest 

 aud most completely formed segments are those next to the old part, 

 and the smallest and least developed at the distal end. 



In contrast to this is another worm from which also about 30 

 segments were cut off (leaving 71 old segments). In this case a new 

 head has regenerated (Jan. 27— May 15). The anterior end re- 

 sembled a head in form (Fig. 5) and is composed of 7 or 8 new seg- 

 ments. Sections show that the ventral cord does not extend to the 

 anterior end of the new part but turns up on each side of the di- 

 gestive tract to join a large dorsal brain. 



In another experiment (Nov. 12— May 15) 20 segments were 

 cut off from the anterior end, i. e., the worm was cut in two just in 

 front of the clitellum. Several of the posterior ends of these worms 

 also developed at the anterior end what appeared to be a tail. One 

 of these is shown in Fig. 6. There are about 17 new segments (and 

 90 old ones). A vertical slit is found at the end of the new part. 

 Sections of this worm show the ventral nerve cord extending to the 

 end of the new part. No brain is present. 



Fig. 5 Fig. 6. Fig. 7. Fig. 8. Fig. 9. 



Several other worms were obtained that also show a number of 

 segments at the anterior end. One of these is shown in Figs. 7—9 

 (Nov. 9[?] — May 15). The new part contains about 35 new segments. 

 There are about 75 segments in the old part. The worm had been 

 cut in two immediately in front of the clitellum and had, therefore, 



