4 C. M. CHILD. 



lies on the bottom of the dish (Fig. 4). If the ring is turned over, 

 a new rotation often occurs, which brings the line of union into 

 approximately the same relative position. As stated in my earlier 

 paper ('096, p. 357), this appears to be an "attempt" at orienta- 

 tion with respect to the substratum, but since the original distal 

 and proximal ends of the piece are united with each other and 

 since, as is evident from the later processes in these pieces, the 

 original polarity is decreased or almost eliminated by this union, 

 any complete orientation is of course impossible. 



Most of these rings give rise in the course of several weeks to 

 groups of tentacles or single tentacles which lie along the line of 

 union, but which may arise wholly on one side or the other, i. e., 

 wholly from the original distal or the original proximal parts, 

 or may involve both in the formation of a single tentacle group. 



In some cases these groups of tentacles are without any close 

 resemblance to the normal disc of Harenactis and they often 

 show a more or less marked bilateral or biradial symmetry with 

 respect to the line of union (Child, '09^, Fig. 10). More com- 

 monly, however, each group shows a more or less distinct radial 

 symmetry, similar except as regards the number of radii, to the 

 symmetry of the animal in nature (Child, 09^, Figs. 12, 15, 

 I 7~3)- I n these radially symmetrical tentacle groups mesen- 

 teries could in many cases be seen distinctly upon the small 

 discs, their arrangement corresponding with the intervals be- 

 tween the tentacles. In some cases these were clearly continua- 

 tions of the old mesenteries (Child, '09^, Figs. 18-20), but in 

 other cases I was unable to find any such connection and was 

 uncertain whether the formation of new mesenteries had occurred 

 or not. 



In my earlier experiments the largest number of tentacles in a 

 radially symmetrical group was seven ('096, Fig. 29^) and in no 

 case were mouth and esophagus present, though in one ring 

 several groups showed a tentacle-like outgrowth in the center of 

 the disc, where the mouth would normally appear. I suggested 

 that this outgrowth might possibly represent an everted esopha- 

 gus, but could not be certain as to its nature. 



These tentacle groups were interpreted as representing new 

 polarities, new body-axes, developing adventitiously in the region 



