B 



FORM REGULATION IN CERIANTHUS. 315 



others and masses of the mesenterial filaments protruded from 

 each end, thus delaying the closure and normal regeneration ; it 

 is therefore omitted from the present consideration. The pieces 

 A and C are nearly equal in length and are about 

 two thirds the length of D. 



October 22 : two days after section : All pieces 

 still collapsed. 



October 23 : three days after section: 

 A. Margin of oesophagus united with body-wall, 

 aboral end closed and enteron partly filled with 

 water. 



C. and D. Both still collapsed. 

 October 24 : Four days after section : 

 A. Sufficiently distended with water to spread 

 the inrolled margins and allow the oesophagus at 

 the oral end and the new tissue closing the aboral 

 end to become visible. I / 



C. and D. Both still collapsed. 



FIG. 6. 



October 25 : Five days after section : 



A. Distended with water : tentacular ridge visible and pigment 

 disappearing from it. 



C. Ends closed by new tissue ; distended. 



D. Enteron partially filled with water ; distension not yet suf- 

 ficient to separate the infolded oral margins and permit new tissue 

 to become visible. 



October 27 : Seven days after section : 



A. Marginal tentacles just appearing on tentacular ridge. 



C. Tentacular ridge distinct ; its pigment disappearing. 



D. Distended with water ; new tissue closing oral end ex- 

 posed by separation of cut margins in consequence of distension : 

 tentacular ridge visible, with fading pigment. 



October 29 : Nine days after section : 

 A. Marginal tentacles I mm. 



C. Marginal tentacles just appearing on tentacular ridge. 



D. Tentacular ridge distinct, without pigment ; no tentacles 

 visible. 



October 3 1 : Eleven days after section : 



A. Marginal tentacles 2 mm. At aboral end new tissue grow- 

 ing out in a small point 1.5 mm. 



