206 University of California Publications in Zoology. [Vol. 6 



After transverse cuts this advance may be so rapid and vigorous 

 as to constrict off a central nub of the axial dome. Such a 

 movement is due undoubtedly to the activity of the circular 

 muscles. Other factors, however, are involved. After oblique 

 cuts, as in the case shown in fig. 1, the contraction of either 

 longitudinal or circular muscles would cause the wound to gap 

 rather than close. 



1 2 



Fig. 1. — Regeneration of a segment of a column three days after an 

 oblique eut. Two days later the tentacles were equivalent and equidistant. 



Pig. 2. — Portion of transverse section of adult of moderate size, some- 

 what contracted, showing relation of axial parenchyma to the epithelium of 

 the canals. X 88. 



In such cases, the edges of the wound are approximated by a 

 local shrinkage in the axial endoderm in the manner described in 

 my paper on the behavior of Gorymorpha. 2 As the axial tissue 

 withdraws, the body wall follows passively. Even after trans- 

 verse section, this factor probably enters to some extent. As seen 



Univ. Calif. Publ. Zool., 2, p. 333, 1905. 



