202 



PKOTOPIiASM. 



be attacbed ; 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 gopd specim«n 

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

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

 hollow box, and the rest of the apparatus 

 is tlien 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 upv 

 current of yvater through the tube 





through the box the rale of the protoplasmic cii'culation is in- 

 creased. The amount of heat applied can be easil}' regulated 

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

 effects of cold, the resei'voir can be placed in a vessel of ice and 

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

 colli water can flow down through the box. 



558. Experiments upon tiie 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 large 



