250 



HEAT AND PROTOPLASM 



[Cn. VIII 



TABLE XXI 



selves with a hand lens, bottles of alcohol for preserving organisms for farther 

 study, and an accurately calibrated thermometer. A source of error to be 

 guarded against lies in the precise determination of the temperature of the water 

 immediately surrounding the organism observed; for in some warm springs or 

 their outlets the surface water is said to be much warmer than the deeper layers 

 in which the organisms are found. Finally, if possible, it would be desirable to 

 determine on the spot, experimentally, the maximum temperature which these 

 organisms can withstand. For this determination some of the methods referred 

 to on p. 220 should be used. 



* Notes on each of these cases will be found at the end of this chapter, pp. 

 263-267. 



