DYNAMICS IN EVOLUTION. 73 



direction of the motion of the whole organism. This maximum 

 vortical flux of the material particles of the amoeboid in this 

 new direction will result in elongating the organism in th 

 direction of the motion thus set up. The elongation of the 

 organism is, therefore, due to the flow of its own particles 

 amongst and through themselves. We are thus made aware 

 ot the fact that this simplest organism is elongated in the 

 direction of its own motions, as a consequence of the continuous 

 readjustment of the internal equilibrium of its parts in respect 

 to influences affecting it from without. The shape of this 

 organism, at every instant of its motions, is, therefore, 

 mechanically caused. 



We may pursue our analyses still further. If we now look 

 down upon such an amoeboid organism from above, when 

 moving upon a plane surface, as in Fig. 4, we find that it is 

 not only elongated in the direction of its motion, but that its 

 anterior end is tensely filled with substance; its outer layer of 

 molecules at the "anterior" end is tensely stretched. At the 

 tail end the organism is wrinkled or papillated; this wrinkled 

 or papillated appearance of the posterior end of the organism 

 is due to physical causes, as the following observation proves: 

 In Fig. 4 there are two anterior pseudopodia, b and c, 

 through which there are fluxes of particles in progress at 

 about the same rate. The vortical current is seen to divide 

 and to flow into both these pseudopodia, thus keeping the 

 outer molecular film over both tense and rounded. Let, 

 however, a disturbance of the surface-tension occur at the 

 end of b, while at the end of c' this disturbance subsides, as 

 in Fig. 5 and there will be a flux of particles out of c' in 

 the direction of the arrow into />, and c' will lose its tense, 

 full outline, and its surface will become wrinkled or papillated, 

 just as appears at the " tail " end of the organism at a. In 

 every detail of the morphology of this organism, we therefore 

 discover that physical or "physiological" agencies are 

 operative in determining its figure. We are, therefore, in a 

 position to affirm, with positive certainty, that the morphology 

 of this organism has little significance until its actions and 

 their physical causes have been studied. This is only one of 



