50 



PATTERNS AND PROBLEMS OF DEVELOPMENT 



RECONSTITUTION AFTER SECTION OBLIQUE TO THE LONGITUDINAL AXIS 



Differences in rate of reconstitution in relation to different levels of a 

 cut end oblique to the longitudinal axis have been observed in a number 

 of coelenterates and planarians. When stem pieces of Tubularia or 

 Corymorpha are cut with plane of section strongly oblique to the longi- 

 tudinal axis, the distal tentacles of the hydranth often develop first at the 



Fig. 23. — Haliclystiis auricula. Lines AA-GG, XX, IT, indicate levels and directions of 

 section (from Child, i933&). 



most oral region and progressively to lower levels, forming a ring of distal 

 tentacles oblique to the polar axis of the stem. In these forms, however, 

 closure of cut ends is rapid, and the oblique surface may become rounded 

 before tentacles develop. When this occurs, distal tentacles develop near 

 the oral end as usual, but the plane of the tentacle ring is transverse, not 

 oblique. 



Difference in rate in relation to an oblique cut surface appears much 

 more clearly in the sessile scyphozoan HaUdystus. After transverse sec- 

 tion at various levels of umbrella or stalk (Fig. 23, AA-EE) reconstitution 



