202 



PROTOPLASM. 



be attached ; these pieces run to a small reservoir of water which 

 can be heated at pleasure by means of a spirit-lamp, as shown 

 in the figure. Suppose a slide to have upon it a good specimen 

 of a stamen-hair ol'Tradescantia, furnished with sufficient water 

 and properly covered. It is placed in the aperture f of the 

 hollow box, and the rest of the apparatus 

 is then arranged as shown in the cut. The 

 rate of circulation of the protoplasm is now 

 carefully observed, and the temperature 

 shown by the thermometer t is also noted. 

 With increments of heat from the upward 

 current of water through the tube and 



through the box the rate of the protoplasmic circulation is in- 

 creased. The amount of heat applied can be easily regulated 

 by the height of the reservoir. If it is desirable to observe the 

 effects of cold, the reservoir can be placed in a vessel of ice and 

 raised above the stage of the microscope, so that a current of 

 cold water can flow down through the box. 



558. Experiments upon the effect of heat can also be con- 

 veniently conducted by means of a less expensive apparatus 

 which consists of a double-walled box of zinc placed on firm 

 supports at the height of a few inches above the table, and hirge 



