288 



HARRY BEAL TORREY. 



substratum. I pointed out some years ago 1 that Corymorpha 

 is negatively geotropic, even small fractions of the column re- 

 acting with great definiteness. This tendency to bend away 

 from the center of the earth can be effective, however, only when 

 the reacting piece is properly anchored. Pieces free from the 



FIG. ii. 



substratum never exhibit the reaction. As soon as they are at- 

 tached, it appears; and U- and Y-shaped figures are formed when 

 pieces are heteromorphic and the point of attachment is between 

 the developing ends. 



FIG. 12. 



Each Y-shaped figure is formed from a straight piece by the 

 development of a protuberance that corresponds to the stem of 

 the Y, and is terminally adhesive (Figs, n, 12, in both of which 

 the limbs of the Y have become much attenuated during the 



1 J. E. Z., i (1904), p. 395; Univ. Calif. Publ. Zool., 2 (1905). P- 335- 



