Viscosity Changes of Protoplasm 171 



enlarged portion near the tip of a pseudopod and then to deflect 

 outward where it sooner or later comes in contact with the edge of 

 the opening in the sac of granular plasmagel where it is caught 

 in the gelation of the fluid in which it is suspended and becomes 

 stationary in reference to points outside, regardless as to whether 

 it is to the right or the left or above or below the plasmasol. As 

 more and more substance from the plasmasol is deposited at the 

 anterior border of the granular plasmagel the ameba moves forward 

 and the observed granule approaches the posterior end where it 

 sooner or later comes to the inner surface of the plasmagel. Here 

 the substance in which it embedded goes into solution carrying the 

 granule into the plasmasol in which it is again transported to the 

 anterior end where it again enters the plasmagel, etc." (See also 

 Fig. 7, p. 409, Mast, 1926.) 



Many questions remain unanswered, such as the regulatory 

 mechanism, the factors involved in solution and gelation, and the 

 origin of the contractility of the gel layer. 



LOCOMOTION OF CELLS 



The migrating mammalian lymphocyte exhibits typical ameboid 

 locomotion. It has a thin gel layer, a central less viscous endoplasm, 

 a persistent posterior end with a hyaline tail bud, and an anterior 

 pseudopodal end. It has, relative to its size, a very large nucleus. 

 The lymphocyte is one of the smallest cells of the body. The thin 

 cortex is not always recognizable, and one infers from the behavior 

 of the lymphocyte during locomotion that this layer must be a 

 contracting gel. Each time a pseudopod appears, a constriction ring 

 develops at its base where it joins the body of the cell. As the 

 lymphocyte advances, the constriction ring remains stationary in 

 relation to a point outside the cell exactly as does a particular 

 granule embedded in the anterior part of the plasmogel of the 

 ameba. As the lymphocyte moves forward, the body of the cell 

 posterior to it gradually decreases in size. The large nucleus as it is 

 forced through the constriction ring is constricted and distorted by 

 the ring, and when it is finally pushed through the ring it regains 

 its original spherical form. It is evidently elastic. When all but the 

 little tail bud has passed through the ring, the latter contracts 

 down and increases the length of the tail which undergoes shorten- 

 ing between each such addition. One cannot see very much of what 

 goes on in the cell. The flowing forward of the few mitochondria 

 can sometimes be seen. There is very little endoplasm and only a 



