FORM-REGULATIONS IN CERIANTHUS. 



2/9 



as compared with about 13.5:1 in the whole. The relation 

 between length of marginal tentacles and length of body is about 

 I :2 while in the whole it is 1:3. The change in the relation 

 between length and transverse diameter in each piece during the 

 experiment consists chiefly in decrease in the latter. None of 

 the pieces except C have increased in length to an amount equal 

 to the growth of new tissue at the aboral end. In other words 

 all but C both length and transverse diameter of the old tissue 

 have decreased but the latter much more rapidly than the former. 

 In the actual decrease in size two factors are probably concerned, 

 viz., loss of substance and decrease in general internal pressure : 

 of these the former is due to starvation and use of material in 



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regeneration, the latter both to approaching exhaustion and to 

 the reduction in temperature which occurred during the course 

 of the experiment from October to December ; both of these 

 conditions reduce ciliary activity and therefore internal pressure 

 also. But these factors alone must bring about a proportionate 

 or nearly proportionate reduction in form. Other factors must 

 therefore be concerned in the change of form which occurs in 

 these pieces. 



It remains then to determine whether or not this change of 

 form is due to some inherent capacity of the protoplasm inde- 

 pendent of external conditions. The first point of importance in 

 the consideration of this question is the dependence of the change 

 of form upon distention with water. Pieces kept open at one or 

 both ends continue indefinitely to grow shorter and smaller until 

 finally they form rounded masses, even though originally the 

 length was many times the diameter ; in short the changes in these 

 collapsed pieces are opposite in character to those that occur in 



