INFLUENCE OF MECHANICAL SHOCK II 



substance on which the organisms were found, under a small bell- 

 jar or moist chamber at a temperature of 20 to 25 ° C. After the 

 spores have germinated and the myxamoeba have attained a size 

 convenient for manipulation, which will need a few days, mount a 

 few in a drop of water on an ordinary microscopic slide at room 

 temperatures. The amoeba secured from a pool of stagnant water 

 or aquarium containing decaying leaves will serve equally well. 

 After the organisms have regained their normal condition and are 

 slowly moving in the field of view tap the cover-glass smartly 

 with a pencil. Note the retraction of the pseudopodia or irregular 

 extensions of the body and the contraction of the entire mass to 

 a more or less rounded form. Note the length - of time before the 

 pseudopodia are again extended. Repeat a number of times. 

 Note appearance and behavior of nucleus and vacuoles. 



The demonstration may be accomplished with almost any 

 plasmodial organism and is doubtless a protective movement for re- 

 ducing the surface to a minimum and thus lessening the liability 

 to injury. The reactions to chemical stimuli of an injurious char- 

 acter are generally similar. 



17. Influence of Mechanical Shock upon the Streaming Move- 

 ments of Vegetative Cells. Mount a sound leaf of Philotria 

 (Eloded), stamen hairs of Tradescantia, hairs from the epidermis 

 of Cucurbita, or Cypripedium, in water at room temperature, and 

 observing streaming movements of protoplasm. Having secured 

 a good view in which the moving strands are to be seen clearly 

 with a magnification of 250 to 300 diameters, rack up the objec- 

 tive slightly, and tap on the cover-glass smartly with a pencil. 

 A heavier shock will be necessary to secure a reaction than was 

 used in the previous experiment, because of the outer protective 

 walls surrounding the protoplasm. Focus again on the same 

 cell as before and note the change in the movements, and the 

 consistency of the protoplasm with respect to its granularity. 

 Allow the preparation to remain on the stage of the microscope 

 for half an hour and examine at intervals of five minutes. Note 

 the period of recovery and the resumption of movement. Com- 



