36o PATTERNS AND PROBLEMS OF DEVELOPMENT 



not be. The most frequent forms of multipolarity, appearing in absence 

 of purposely applied experimental conditions other than isolation of 

 pieces by section, are multiphcations of manubria (Fig. 120). Each manu- 

 brium is normal and complete in form from its apical region as far basip- 

 etally as it develops, and each can be shown by the various methods 



H I 



Fig. 120. — Multipolar forms of Corymorpha (from Child, igibb, 192 ;«) 



available to constitute a gradient pattern with high end apical. Forms 

 with numerous manubria usually develop from proximal stem-levels where 

 the diameter is greater than distally. Section at these levels often involves 

 more crushing and laceration, and closure of the cut end is less rapid and 

 regular than distally. The multiple manubria are apparently determined 

 by local differences in activity of cells or cell groups on the end of the 

 piece. There is some evidence that the longitudinal entodermal canals 



