76 BIOLOGICAL LECTURES. 



the vortex-current of particles into diverging currents, the 

 summation of the motions of which may, when the organism 

 is moving on a plane surface, become resolved mechanically 

 into a single motion of translation in one direction. 



When the organism is freely suspended in water it protrudes 

 pseudopodia equally in every direction and assumes a globular 

 figure, somewhat like a Heliozoan or Radiolarian, because 

 its surface-tension is now being disturbed at nearly equallv 

 separated points over its whole surface. It therefore falls into 

 a condition of spherical equilibrium, since the components of 

 all the surface-tensions are resolved at the centre of the 

 organism. The moment it touches a fixed surface, distortion of 

 the formerly globular organism takes place under the influence 

 of gravity and adhesion, and the vortical flux of particles that 

 is now set up is different in nature from that which took place 

 in every direction when it w^as in the suspended globular con- 

 dition. There is at once a maximum flux of particles in the 

 direction of the point at which the most active disturbance of 

 surface-tension occurred, and the resulting current becomes very 

 massive so that the whole contents of the organism, except the 

 nucleus and water vacuole, flow forward as a massive pseudopod, 

 that is somewhat flattened or depressed by the action of gravity 

 and adhesion, but which is much larger than any of those 

 produced while in the spherical condition. How little \'erworn 

 has appreciated and understood these complex jirocesses may 

 be judged by any one who has read his work on the motion of 

 livimr substance. He has affirmed what does not exist in 

 regard to small Amceba protcnx, where the flux is continuous 

 and where no retreat of particles to the nucleus, such as he 

 postulates, can take place for hours together. In short, 

 Verworn has totally failed to understand the real significance 

 of these complex phenomena. Greef, also, has made assump- 

 tions with regard to amoeboid motion, especiall}' the existence 

 of muscular fibrils, which by no stretch of the imagination can 

 be conceived to hold of the proteus animalcule. 



Verworn has also failed to understand the physical reasons 

 why small blebs or pseudopodial warts Avere produced along the 

 sides of a retracting pseudopod. He speaks of " stimulation " 



