72 BIOLOGICAL LECTURES. 



equilibrium, due to its own gravity, its viscosity, and the 

 force with which the particles on its under side tend to adhere 

 to the fixed solid surface upon which it rests. The upper part 

 of the mass now falls into an equilibrium determined by the 

 surface-tension of its superficial molecules and the viscosity or 

 reciprocal friction of the latter upon each other. Gravity, 

 viscosity, surface-tension, and adhesion are the four cooper- 

 ating agents that now determine its figure. So long as it was 

 floating or suspended in the water, the influence of gravity 

 and adhesion operating in relation to a fixed surface were 

 excluded. We thus see how completely this organism is 

 the creature or subject of energy-conditions in this state. 



In the next phase of its motions this is still further 

 illustrated. In Figs. I and 2, short, blunt pseudopodia are 

 being protruded in all directions; but in Fig. 3, the sequence 

 of events changes, and the organism begins to take up its 

 march by means of a vortical flux of its substance across the 

 surface upon which it rests, and in the direction of the arrow. 

 Surface-tensional disturbances of greater magnitude have evi- 

 dently affected the right side of the mass, and one or more of 

 the small original blunt pseudopodia at this point have been 

 merged into a strong, single " anterior," pseudopodal current, 

 in which a maximum flux of molecules is taking place in the 



