FORM REGULATION IN CERIANTHUS. 3 



Since I am convinced that the power of regeneration is due, 

 not to any special regulatory mechanism, but to those properties 

 of organized matter which cause "normal" or "typical" growth 

 and differentiation, I believe that the differences in regenerative 

 power and the differences in normal anatomical and physiological 

 reactive capacity must all depend, at least in some degree, on the 

 general reactive capacity of the tissues. 



The differences in reactive capacity in different regions may be 

 due to differences in the intensity of metabolic change, or they 

 may depend upon other conditions. It is of interest to note in 

 this connection that the differentiation and concentration of ner- 

 vous tissue is greatest about the oral end in the actinians. It is 

 at least not impossible that this fact is correlated in some manner 

 with those above mentioned. For the present, however, the pos- 

 sibility of such a correlation is merely suggested as the data are 

 still insufficient for positive conclusions. 



There is also a possibility that the difference in the rapidity 

 and amount of regeneration at different levels may be due in part 

 to differences in internal pressure resulting from circulatory cur- 

 rents in the enteron. Discussion of this phase of the problem is, 

 however, reserved for a future time. 



The Factor of Size. 



My observations along this line are to a large extent merely 

 incidental, since, owing to the relatively slight influence of this 

 factor, its effects were not clearly recognized until it was too late 

 to complete the series of experiments necessary for further study. 

 Certain conclusions may, however, be drawn from my work and 

 these are briefly mentioned here. 



It is evident from Series 54 and 55 that great differences in size 

 of pieces do not affect the rapidity of regeneration in earlier 

 stages. The pieces 54^ and 55^4, although widely different in 

 size, regenerate orally with equal rapidity except in the final 

 stages. Aborally the smaller piece regenerates more rapidly than 

 the larger because its aboral end lies in a region of greater cellu- 

 lar activity. As regards the total amount of regeneration at both 

 ends the small piece exceeds the laige piece, because of its posi- 

 tion in the parent body. The only effect of size was noted 



