LEECHES 45 



as compared with the pleotropic movement 

 (through the water), and is derived by inheri- 

 tance from swimmers. 



In the same strain, referring to Amphioxus, 

 Dr Eisig {loc. cit., p. 276) says that however 

 primitive one may hold its organisation to be, 

 yet nobody will assert that its limbless body and 

 its predominantly cryptoid locomotion represent 

 archaic features. I am unable to follow these 

 conclusions myself, as I approach this matter 

 independently from a cryptozoic and stereo- 

 tropic standpoint ; and in this, as in many 

 another affair, everything depends upon the 

 point of view. The facts are undeniable, but 

 the way of dealing with them cannot be other 

 than arbitrary. 



Another instructive example of the association 

 of stereotropism of a highly specialised type with 

 well - marked pleotropism is afforded by some 

 leeches. The stereotropism of the medicinal 

 leech is of such a nature that it has passed into 

 a proverb. Closely connected with this habit 

 is its method of obtaining its food by sucking 

 the blood of vertebrates. It progresses along a 

 hard surface by the looping gait, and can also 

 swim rapidly by vertical undulations of the body. 

 The land leeches of Ceylon and Japan belong to 

 genus Hcemadipsa. They also, as mentioned 

 above, feed upon the blood of vertebrates, for 

 which they exhibit a remarkable propensity 



