DYNAMICS IN EVOLUTION. 75 



The manner in which the successive rents in the outer 

 molecular skin of the organism are produced is such that a 

 sudden rupture occurs through which a fresh outpour of 

 substance happens over which a new molecular skin is instantly 

 formed continuous with the ruptured edge of the old. These 

 rents do not take place in relatively the same place in succession. 

 For example, rents may occur in the outer film one after the 

 other at points a little off of the extreme central point of the 

 " anterior " end, and alternately a little to the right and left side 

 of the latter. The vortical flux is thus thrown slightly aside 

 alternately to the right and then to the left, then to the right, 

 then to the left again, and so on, indefinitely. It thus results, 

 however, that the summation of these alternating outbursts of 

 substance become the components of the aggregate motion of 

 the whole organism in one general direction. 



If a rent occurs at one side of the organism, due to a 

 disturbance of surface-tension at an anterior lateral point, a 

 lateral flux of particles may thus be set up, as a result of 

 which the entire contents of the organism may be sucked up 

 ''anteriorly" and "posteriorly" to the point where the new 

 outflow has taken place. In other words, the "head" and 

 " tail " ends of the organism may be thus caused to flow in 

 opposite directions into the lateral outburst and the whole 

 organism take a new direction of motion with all its parts 

 oriented in respect thereto. Amceba protcns, therefore, cannot 

 move except by developing a vortical flux of particles, and 

 it therefore is a "living" vortex-ring of particles. These 

 outbursts, in large individuals, occur successively at short 

 intervals of time, so that the motion of the creature is 

 fitful. In young protcus animalcules the bursting out or 

 pouring forth of the plasma at the "anterior" end maybe 

 continuous, so that the motion is uniform and an ideally perfect 

 type of the "living" vortex-ring of particles is realized. 



Every pseudopodium is, however, so long as it is being 

 protruded, a vortex-current in which the motion of the particles 

 is swiftest at its center and at its tip, while at the sides the 

 particles are quiescent and form a shell through which the 

 central ones are moving. The pseudopodia, therefore, divide 



