84 VITALISM AND SCHOLASTICISM 



unless the wind or the rain or the action of 

 some other force cause it passively to be 

 moved. Atoms of non-living material thrown 

 into water will sink or swim according to their 

 specific gravity, and if they are capable of 

 floating they will be borne down stream or 

 hither or thither as the currents in the water 

 may determine. But the living animal, even 

 of the lowliest character, swims, if it chooses, 

 and it generally does choose, against the stream, 

 whether it does this like the amoeba by the 

 putting forth of temporary processes, or like 

 the ciliata by the waving of tiny permanent 

 projections, or like the fish by the aid of its 

 fins. 



This tendency to move against the stream is 

 Rheotaxy called rheotaxy. But thus to name the capa- 

 bility or further to tell us that one of the 

 characteristics of living matter is to react in 

 this way to running water is not to explain the 

 occurrence. Many people are satisfied if they 

 have named a phenomenon and others are quite 

 happy if they have restated the terms of the 

 occurrence in fresh phraseology, but it must 

 be quite obvious that neither of these processes 

 helps one very far along the road which leads 

 to an explanation of the process itself. 



Let us, however, suppose for a moment, that 

 the so-called rheotaxy is really a reflex action 



