L. V. MORGAN. 



will be noted that in all the cases described where regeneration 

 occurred without the ganglia, some of the old tissue anterior to 

 the level of the ganglia was left in the piece. The difference in 

 regeneration with and without some anterior tissue was strikingly 

 shown in the following experiment : the cephalic ganglia were 

 removed with a straw, and the worm then cut in half longitudi- 

 nally, the left half through an accident was injured, and some of 

 the anterior tissue broken off. After seven weeks, the right half 

 had regenerated well, and had for two weeks shown two distinct 

 eye-spots, as in numbers of other similar cases. The left side, 

 kept in the same dish for the same length of time, showed less 

 regeneration, and no eye-spots had appeared, nor could any be 

 found in sections (Fig. A, 5^, $d}. In all the cases where re- 

 generation occurred in the absence of the ganglia, the cuts were 

 made in such a way that lateral regeneration without anterior 

 regeneration might account for the restoration of the form of the 

 worm. 



Regeneration of the anterior tip of the worm, that is when the 

 worm has been cut off anterior to the ganglia, occurs in the ab- 

 sence of the ganglia as well as when they are present. The 

 ganglia of several worms were removed with a straw, and after 

 a few days, when the wound had closed, the anterior end was cut 

 off anterior to the scar. Regeneration occurred as in check ex- 

 periments, where the ganglia were retained, and by the time the 

 eye-spots had reappeared, the form of the worm was completed 

 (Fig. A, 6). 



SUMMARY AND CONCLUSIONS. 



The experiments show that : 



1. Pieces containing the cephalic ganglia behave like normal 

 animals, and regenerate readily. 



2. Pieces deprived of the ganglia are sluggish, and may or 

 may not partially regenerate. 



3. Pieces cut across at any level posterior to the ganglia, do 

 not regenerate to any extent anteriorly ; but 



4. Pieces deprived of the ganglia in such a way that some 

 tissue anterior to the level of the ganglia remains in the piece, 



