1 88 L. V. MORGAN. 



of the head with a straw), containing the eye-spots and cephalic 

 ganglia and very little tissue besides, responded readily to light 

 and touch, and crawled actively ; in all cases in which such pieces 

 survived, they quickly regenerated tissue in every direction, and 

 in less than two weeks presented the appearance of small worms 

 with heads very large in proportion to their tails (Fig. A, 7, 8). 

 Pieces without the cephalic ganglia, on the other hand, behaved 

 differently. They were sluggish in their movements, responded 

 slowly and did not even stay under water, but were often found 

 dried up on the sides of the dish. Also, as Child and Schultz 

 found in the forms which they studied, anterior regeneration took 

 place only to a very limited extent. Pieces cut at any level 

 posterior to the ganglia often healed in such a way as to 

 apparently prevent the growth of new tissue. After the worm 

 was cut, the sides stretched very much and actually met in front 

 of the worm, bringing the two halves of the cut surface in con- 

 tact, so that they grew together, the point where they met in the 

 middle line being raised above the level of the surface on which 

 the worm crawled. To avoid such a closure of the wound, 

 worms were in some cases cut so that the anterior end was pointed, 

 or else the pieces were kept flat in vaseline under water. Even 

 so, scarcely any anterior regeneration took place. When the 

 posterior end of the same piece was also cut off, it was rapidly 

 regenerated, proving, as in Drendroccelum, that growth in the 

 anterior direction was not wanting because of a general lack of 

 power to regenerate in the absence of the cephalic ganglia. The 

 pieces were not kept long enough to prove that anterior regen- 

 eration never could occur, but, whatever the limit, the rate is 

 excessively slow as compared with the rate in other directions or 

 in other sorts of pieces. One worm which was supposedly cut 

 behind the brain, completely regenerated the anterior end includ- 

 ing ganglia and eye-spots. It is undoubtedly true that it was 

 cut posterior to the eye -spots, but the probability is that part at 

 least of the ganglia remained. That this would be possible can 

 readily be seen from the figure of a horizontal section of a normal 

 worm, showing the relative positions of ganglia and eye-spots.* 



* As this paper goes to press, a new paper has appeared by C. M. Child, " Studies 

 on Regulation, VI., The Relation Between the Central Nervous System and Regula- 



