AMCEBOID MOVEMENT. 201 



In the naked protoplasm of M^-xomj-cetes the rates of move- 

 ment of the currents are much greater, as Hofmeister shows by 

 the following examples : — 



mm. per minute. 



Dijymium Serpula 10. 



Physarum .species 5.4 



554. The above rates are not constant even in the same speci- 

 men ; after having been uniform for a few minutes, the rate 

 maj- slowly diminish for a time, the temperature and other con- 

 ditions remaining apparently unchanged, and then as slowly 

 increase until the maxinuim is again reached. Again, the rate 

 is subject to sudden clianges. In general, however, it is nearly 

 the same for the same part of a given plant. 



555. The amoeboid moTement in naited protoplasm is rather 

 more sluggish than the circulation, as the following figures from 

 Hofmeister show : — 



mm. per mlnate. 



Didyinium Serpula 0.4 



Physaruni sp 0.29 



Stemonitis fusca . 0.15 



The far more rapid movement of ciliated protoplasmic bodies 

 will be described under "Movements." 



556. The effects upon protoplasm of various agents — for in- 

 stance, heat, light, electricity, etc. — can be studied in the same 

 cells in which the movements are observed ; in fact, their effects 

 upon the movements themselves are among the most striking 

 phenomena noticed. It must be remembered, however, that in 

 experimenting upon the protoplasm in cells which arc furnished 

 with a cell-wall and provided with cell-sap, other factors are 

 present than those which must be taken into account in deal- 

 ing with the naked protoplasm of plasmodia. And hence it is 

 proper in most cases, in interpreting the results obtained in 

 experiments upon the protoplasm of cells, to speak of the effects 

 of the agents upon the cells themselves. 



557. Relations of protoplasm to heat. In experimenting upon 

 the effect of heat on protoplasm, the apparatus generallj' em- 

 ployed is the so-called warm chamber. In its simplest form this 

 consists of a hollow-walled box, having a slit in which a slide 

 can be placed, and at the centre of the upper and lower walls 

 holes of the same size as the largest diaphragm of the micro- 

 scope, so as to allow light to pass from the mirror directly 

 through tiie slide and thence to the objective. Connected with 

 the box are two tubes to which pieces of rubber tubing maj' 



