THE ACTIVITIES OF CORYMORPHA 309 



contractile, whereas such fibers are invariably present in that 

 part of the stalk distal to the buried portion. The contraction 

 of the stalk on its long axis must, therefore, be attributed to the 

 action of its longitudinal muscle. 



When the distal end of a decapitated stalk is examined, a 

 plug of large vacuolated cells is seen to protrude from it. 

 These cells, well known to the earlier students of Corymorpha, 

 fill the axial part of the polyp and serve to a certain degree 

 as a skeletal tissue. When the polyp contracts longitudinally, 

 they are crowded together lengthwise and on relaxation they 

 doubtless tend to return the stalk to its originally elongated 

 shape. But this operation is probably much facilitated by the 

 action of the circular muscle of the stalk, whose contraction 

 would crowd the mass of axial cells back to its elongated form 

 and thus restore the stalk to its original shape. Thus by the 

 alternate action of the longitudinal muscle and the circular 

 muscle on the mass of axial cells the contraction and elonga- 

 tion of the stalk is accomplished. 



If live decapitated stalks of Corymorpha are placed in sea- 

 water containing magnesium sulphate or chloretone, they soon 

 become incapable of longitudinal contraction. The stalks re- 

 tain what would be called the elongated condition. If one 

 of these anesthetized stalks, particularly one that has been 

 treated with chloretone, is vigorously proded at a given spot 

 with a blunt rod, though no longitudinal contraction occurs, 

 in the course of three-quarters of a minute to a minute a con- 

 stricted ring appears on the stalk and remains there for from 

 five to eight minutes. If the same experiment is tried with 

 a stalk that has not been anesthetized, the stalk immediately 

 contracts lengthwise but elongates soon afterwards, during 

 which a ring of constriction appears and may remain evident 

 for as much as ten minutes. 



As the constriction rings produced in these tests must be 

 the result of the contraction of localized parts of the circular 

 muscle and as their formation is quite independent of anesthet- 

 ization, it follows that the longitudinal and circular muscles 

 must act upon very different principles. The longitudinal 



