FORM-REGULATION IN CERIANTHUS. 



were slit longitudinally on one side. Thus these pieces resemble 

 those of Series 11 and 17 (Fig. 8) except that a few millimeters 

 at the aboral end have been removed. The object in the re- 

 moval of the extreme aboral end in pieces was to avoid if pos- 

 sible the transverse inrolling from the aboral end which was so 

 frequent in Series 11 and 17 (Figs. 10 and 12) and which inter- 

 feres greatly with closure. In this series then the object was to 



FIG. 12. 



FIG. 13. 



FIG. 14. 



FIG. 15. 



FIG. 16. 



FIG. 17. 



delay closure for a time but not to make it impossible. The 

 experiment was continued for about four months and during that 

 time all of the pieces closed and acquired essentially the typical 

 form of the species. 



October j. 7 days after section. None closed ; variously 

 rolled ; only two with any traces of tentacle buds. 



October 10. 14 days after section. Six pieces with tentacles ; 

 three pieces still without any traces of tentacles. 



From this point on it will be convenient to give the history of 



