372 



PATTERNS AND PROBLEMS OF DEVELOPMENT 



gether about the whole circumference, and union results, forming a closed 

 ring like the inner tube of an automobile tire. Usually these rings undergo 

 a rather remarkable orientation which brings the line of union of distal 

 and proximal ends onto the upper surface as the ring lies. Along or ad- 

 joining the band of new tissue uniting distal and proximal ends tentacles 

 and tentacle groups, varying in number and arrangement of tentacles, 

 develop from either distal or proximal side of the union or from both, and 

 in some cases there is approach to development of an actinian axis 



^1^ 

 //[\\ 



A 



B 



Fig. 125, A-E. — Determination of new axis by a lacerated lateral incision in Corymorpha. 

 A-C, incision, later outgrowth and early hydranth; D, induction by the new dominance of a 

 basal region from the opposite side of the original stem; E, development of a basal end with 

 perisarc and stolon buds from a lacerated incision under slightly inhibiting conditions (from 

 Child, 1927c). 



(Fig. 126, A-C). Some of the tentacle groups are bilateral, others radial, 

 and still others irregular. Examination shows that the tentacles of these 

 groups are localized between the regenerating mesenteries and that the 

 form of the group depends on the positions of the mesenteries on the two 

 sides of the line of union and the directions in which particular mesenteries 

 happen to grow toward the line of union. When there is definite axiate 

 outgrowth, as in Figure 126, C, some of the mesenteries reconstitute with 

 the outgrowth and determine the number of tentacles at its apical end. 

 The groups appear to be localized where reconstitutional activity is 

 greater. 



After local laceration of distal and proximal cut ends of the body wall 



