46 FREE AND FIXED ANIMALS 



which might almost be raised to the rank of 

 a tropism. Professor C. O. Whitman has 

 published observations on the Japanese land 

 leech, 1 some of which I have confirmed for the 

 Ceylon land - leech, including the fact that it 

 cannot swim ; it is entirely stereotropic. It 

 has the power of repairing or closing severe 

 wounds, but cannot regenerate the head or the 

 posterior sucker. The lack of the capacity for 

 regeneration in leeches is paralleled by the 

 similar behaviour of Amphioxus. Leeches offer 

 as strong a contrast to other Annelids in this 

 respect as Amphioxus does to the Entero- 

 pneusta. 



The loss of the posterior sucker puts an end 

 to the looping gait but not to the effort to 

 achieve it, and the lack of adhesion behind is 

 compensated by peristalsis on a level surface, 

 and by the great power of extension possessed 

 by the forebody when climbing up a vertical 

 surface. On placing two leeches on a stone in 

 the middle of a large dish of water they remained 

 motionless in a sub - erect attitude, resting upon 

 the hind-sucker for some time, and then descended 

 into the water, looping along the bottom to the 

 side of the vessel. When watching them by 

 candle-light they would not venture across until 

 the light was removed. 



1 Quoted in the Cambridge Natural History, vol. ii., 1896, 

 "Earthworms and Leeches," by F. E. Beddard, p. 408. 



