FORM REGULATION IN CERIANTHUS. 63 



Figs. 10-21 require little explanation. Here transverse con- 

 tinuity is interrupted by a longitudinal cut on one side. The 

 form of the piece after inrolling is at least in large part a matter 

 of chance, being dependent upon the relative rapidity with which 

 the different margins roll inward. 



In Fig. 1 1 the inrolling at the ends has been less than in 

 Fig. 14 and the resulting form is different. In Figs. 1721 the 

 spiral form is due simply to the fact that one longitudinal cut 

 margin rolled inward somewhat more rapidly than the other. 

 An oblique spiral results from more rapid inrolling of the longi- 

 tudinal margin near one end. It is clear that various conditions 

 such as the degree of contraction of the muscles of a certain part 

 of the body, the resistance offered by the mesenteries, the posi- 

 tion of the piece in the aquarium, etc., may constitute conditions 

 affecting the result. 



The frequent rolling about a transverse axis of longitudinal 

 strips cut from the body is clearly the result of the predominance 

 of the longitudinal component of tension. It is interesting to note 

 that this transverse rolling occurs only when the muscles are 

 fully relaxed. If the piece be stimulated sufficiently to cause 

 strong muscular contraction more or less complete unrolling 

 often occurs. Pieces of this sort frequently roll about a longi- 

 tudinal axis after cutting while the muscles are more or less con- 

 tracted and then as the muscles relax after a longer or shorter 

 time begin to roll transversely and continue until completely 

 rolled up in a single or double spiral. 



In cases of spiral or transverse inrolling (Figs. 17, 19, 23, 24) 

 there is little resemblance to an adaptive reaction. As will 

 appear, typical regeneration is impossible in these cases. Since 

 it is scarcely to be supposed that in pieces of a certain form the 

 reaction is adaptive in nature while in pieces of other forms it is 

 due merely to elasticity it is preferable at least to attempt to 

 analyze the apparently adaptive reaction. In the present case I 

 think the analysis has demonstrated that the various methods of 

 inrolling are all explicable on the basis of elastic contraction of 

 the mesoglcea. The apparently adaptive character of the inroll- 

 ing in cylindrical pieces where it results in more or less perfect 

 closure of the ends is due to the particular physical conditions 



