Viscosity Changes of Protoplasm 173 



gel layers would change the contractile tension and produce the 

 wavy motion. The motion of cilia, fibrillae, and imdulatory mem- 

 branes in general can be fitted into the idea that slight changes in the 

 viscosity of gel layers or gels alter the contractile tension which they 

 automatically exert because they are in the gel state. 



LOCOMOTION OF SLIME MOLD {Phijsarum Polycephalum) 



In studying the slime mold one should distinguish, as Howard 

 (1931) suggests, between growth, spreading, and locomotion. Growth 

 is actual increase in the mass of the protoplasm and is presumably 

 accompanied by nuclear division. Spreading may or may not be 

 accompanied by growth and locomotion. Locomotion is always 

 accompanied by spreading at the anterior end. 



The minute pieces with which I propose to deal are examples 

 of locomotion and spreading. Most of the pieces for my prepara- 

 tions were made from the tips of the plasmodia that had spread out 

 over the surface of the water in the Petri dish (100 X 15 mm.) 

 cultures during the preceding night or on the same day from the 

 elevated filter paper at the center on which there was a generous 

 supply of oatmeal. There were considerable differences in the 

 age of the cultures, in the growth, and in the spreading. There were 

 likewise great differences in the behavior of the small pieces in the 

 different preparations. The pieces (6-12) in each preparation were 

 always from the same tip and as a rule behaved in much the same 

 manner. I have not as yet attempted to investigate carefully the 

 relation of the condition of the culture and the type of preparation 

 obtained from it. There are such very great differences in the 

 behavior of the pieces that an investigation of their relationship to 

 the condition of the culture and to the part of the plasmodium from 

 which they are taken must yield some very interesting results. 

 The preparations were made by taking a few millimeters from the 

 spreading tip of the plasmodium with a pair of forceps, transferring 

 to a small Petri dish with water and tearing up into smaller pieces 

 3 to 4 millimeters long. One of these was transferred to a thin 

 spread-out drop of water on a clean cover glass and then teased or 

 cut up with the needles into pieces a millimeter or less in diameter. 

 The cover glasses were sealed in the usual hanging drop manner over 

 a hollow slide or ring. 



Small pieces show at first no or almost no internal movements 

 of endoplasm, due either to complete or almost complete gelation as 

 a result of the mechanical stimulation of tearing with the needles. 



