70 BIOLOGICAL LECTURES. 



within the body of an amoeboid, amongst its molecules, are 

 responsible for disturbances of the surface-tension at one or 

 more points over its surface. It is certain that the chemo- 

 tropism, or affinity for oxygen of its surface molecules, as Ver- 

 worn holds, is essential to this; but we must remember that in 

 order to call forth local disturbances of surface-tension in this 

 way, there must also be a locally exaggerated chemotropism, or 

 affinity for oxygen, at some one point on the surface of the 

 organism. This point has apparently not been made clear by 

 Verworn, but it is essential to a clear understanding of the 

 processes presently to be described. How the positions of 

 such local disturbances of the chemical complexity of the sur- 

 face-layer of molecules of an amoeboid are determined, we do 

 not know. That they are definitely determined, according to 

 some definite law, we may be certain. 



As every one knows who has ever watched a proteus animal- 

 cule under the microscope, the "anterior" pole of the creature, 

 for the time being, is tensely filled with its own substance, so 

 as to present a rounded, full "anterior" extremity while in 

 motion. "Posteriorly," on the other hand, the creature is 

 found to present a wrinkled, partially collapsed appearance. 

 A study of the motions of the organism discloses the fact that 

 its substance is flowing through itself. The central jxirt of 

 this current is moving most rapidly along the middle of the 

 body, while toward the sides it is observed to become progress- 

 ively slower until the outer layers of its substance, along the 

 sides of the creature, are seen to come to rest. It thus results 

 that the outer layers of molecules, along the sides, form a sort 

 of shell or tunnel through which the central current flows. 

 This flux, however, means that there must be a continual or 

 fitful rui)ture of the "anterior" end of the organism in order 

 to let some of itself escape out of itself in front, in order to let 

 some of itself flow into itself behind, in order that some of 

 itself may thus continuously flow through itself in order to 

 make the progressive forward motion of itself possible. In 

 this way the substance of the "posterior" jxirt of the organism 

 can be picked up and carried through the tunnel-like physical 

 shell, formed of the outer layers of molecules of the organism. 



