FORM-REGULATION IN CERIANTHUS. 



107 



On the other hand, if the cut is below the oesophagus the only 

 possible union is body-wall and body-wall (Fig. 10). If the ani- 

 mal is left undisturbed the cut will close in the typical manner, 

 and as soon as distension occurs the relations of parts are once 

 more normal in all essential respects (Fig. 11). Both Loeb and 

 myself agree that under these circumstances a formation of a sup- 

 plementary disc is not possible. 



It now remains to consider how conditions are altered if the 

 animal is inserted into a mesh of the netting (see above, p. 95), 



FIG. 10. 



FIG. 13. 



Fn;. ji. 



FIG. 14. 



IG 9. 



FIG. 12. 



FIG. 15. 



used by Loeb to cause the appearance of the supplementary 

 disc. In Figs. 12, 13 and 14 the result of using the netting is 

 shown. As long as the body is collapsed the netting has little 

 effect (Fig. 12). Indeed, in my experience collapsed specimens 

 react much less readily than others, and orientation in the 

 netting rarely occurs until the animal is at least partly dis- 

 tended. It follows from this that the formation of supple- 

 mentary discs after use of the netting is not necessarily due to 

 delay in closure. As distension with water gradually occurs 



