Viscosity Changes of Protoplasm 111 



The diameters of tubes differ as do also the thickness of the gel walls 

 and the diameter of the endoplasm. There are probably some definite 

 correlations between the size of a tube and the size and rate of 

 increase in size of the anterior region of the plasmolet to which the 

 tube delivers endoplasm and the amount of endoplasm which streams 

 through it. Tubes undergo changes in size. The thickness of the gel 

 walls differs both absolutely and relatively as regards the diameters 

 of the tubes and the diameters of the endoplasm. There is probably 

 a definite correlation between the thickness of the gel wall, the 

 viscosity of the gel, the size of the tube, and the internal pressure 

 of the endoplasm. There can be no doubt about the gel state of the 

 tube wall. Camp found it tough when stuck with a needle. In the 

 large culture dishes numerous ends often stick up into the air. 



The tubes usually contract, that is, decrease in diameter and 

 length, during each forward flow of the endoplasm, and expand dur- 

 ing each backward flow, but not to their previous posterior extension. 

 The tubes are built up anteriorly by transformation of channels in 

 the transition zone. 



Sometimes the endoplasm flows back and forth for a short time 

 without much of any change in the thickness of the gel wall, but 

 within a few minutes the same tube may show solation along its 

 inner surface with each forward flow and gelation with each back- 

 ward flow. This is not always confined to the inner surface, for 

 minute streams in and out of much of the thickness of the wall can 

 be detected here and there. Sometimes projections on the inner 

 surface of the tube deflect the stream of endoplasm for varying 

 lengths of time. Such projection seems to be due to quite local and 

 temporary increases in viscosity and contractions. The general 

 behavior of the tube is thus similar to the posterior end and acts 

 with it as a unit. 



Tubes frequently have an outer hyaline zone, but this often 

 comes and goes as at the posterior end. The hyaline border is usually 

 uneven and more marked on the plasmolets of some preparations 

 than others. Sometimes a tube with a rather thick hyaline zone will 

 in the course of a few minutes lose it entirely, or part of it, and 

 the granular protoplasm will extend to the very periphery. My 

 explanation of the origin of the hyaline border is the same as that 

 of the hyaline cap of Mast. The granular gel layer at times permits 

 clear granule-free endoplasm to be squeezed through its pores to 

 the surface under the interface membrane. Here it gels or partly 

 gels. With subsequent changes in the viscosity of the granular and 



