FORM-REGULATION IN CERIANTHUS. 139 



pieces the inrolling occurred in such manner that the elasticity of 

 the new tissue was insufficient to approximate the cut edges. 



November 20. --68 days after section. Tentacles of the 

 closed piece 1-2 mm.; scarcely visible on other pieces, which 

 are still open. Fig. 1 1 shows the closed piece as it appears at 

 this time. The figure is drawn to same scale as Fig. 9, thus indi- 

 cating marked decrease in size. The longest tentacles on the spe- 

 cimen are opposite the longitudinal cut ; on each side of the cut 

 the tentacles are very short ; all tentacles are rather blunt. The 

 new tissue uniting the edges of the cut is indicated by stippling. 



This piece lived until December 28, and one of the others 

 until December 12. During this time they become still- farther 

 reduced in size, but the second piece never closed. 



Certain of the special features of this series require brief com- 

 ment. It will be noted that even after closure the tentacles of 

 the closed piece did not grow to any great extent, although some 

 growth did occur. This failure to grow is probably due to the 

 exhausted condition in consequence of absence of food. This 

 may effect the power of growth, i. e., the reactive capacity of the 

 tissues, or it may cause a decrease in the water-pressure in one 

 or both of two ways ; first, it is quite probable that soluble prod- 

 ucts of katabolism accumulate in the enteron much less rapidly 

 than earlier, owing to the decreased metabolism ; if this is 

 the case diffusion of water into the enteron and consequently 

 distension of the enteron will be much less rapid : on the other 

 hand there can be little doubt that the beat of the cilia is less 

 powerful in these nearly exhausted specimens than in normal in- 

 dividuals. This being the case, it is easy to see that the inward 

 current through the siphonoglyphe is not capable of maintain- 

 ing as high internal pressure as in a normal animal : moreover, 

 the local circulatory currents into the tentacles must also be less 

 powerful. It is not improbable that all three of these factors 

 play a part in the result ; the osmotic factor is more important 

 before the mouth is formed, decreased ciliary power afterward. 



Series ij. 



September 14, 1902. - - Eight specimens were cut in the same 

 manner as in Series' 1 1 (Fig. 8) and allowed to remain undis- 

 turbed after section. 



