Factors of Form Regulation m Harenactis Attenuata 485 



oesophagus together. This result occurs with the same certainty 

 at the aboral as at the oral end (Fig. 13), though closure of the 

 aboral end in this manner renders a return to the normal form 

 absolutely impossible and the animal is condemned by its own 

 reactions to a death by starvation since there is no opening between 

 the enteron and the exterior. 



On the other hand, in the suboesophageal region the plug of 

 muscles and mesenterial filaments which is forced out of the wound 

 by the contraction (e.g., Fig. 14) often serves to prevent absolutely 

 the closure of the wound. The formation of the "rings" (Fig. 15) 

 when these plugs are cut away has been described above: these 

 rings are as naturally and necessarily the result under certain 

 conditions of the contraction following the w^ound as is the "nor- 

 mal" method of closure under other conditions. 



Contraction follows longitudinal w^ounds just as it does trans- 

 verse, but in longitudinal wounds of considerable length closure 

 almost never occurs, simply because there is nothing in the struc- 

 ture of the animal which serves to bring the cut edges together. 

 Often in such cases the body rolls up in a spiral about either a longi- 

 tudinal or a transverse axis and closure becomes absolutely impos- 

 sible. Figs. 10-24 of my Cerianthus paper (Child '04a) show 

 some of the reactions to longitudinal wounds in Cerianthus. In 

 Harenactis the results are in general similar, though more or less 

 modified by the greater volume of the enteric organs. 



In short, if we limit our consideration of the wound-contraction 

 to certain cases it may seem to be more or less "teleological," 

 but if we include all cases it becomes evident at once that the result 

 of the reaction differs very greatly according to conditions, even 

 in some cases making continued existence impossible. 



The growth of new tissue following the wound does not appear 

 to be an adaptive or teleological reaction any more than the con- 

 traction of the tissues. The conditions under which it occurs 

 have been described above; apparently it occurs wherever these 

 conditions exist, without any relation to the result produced. 

 The growth of new tissue between the cut margins of oesophagus 

 and body-wall occurs as readily at the aboral (Fig. 13) as at the 

 oral end of a piece, although in the former case continued existence 



