RELATIVE STABILITY OF LIVING MATTER 



313 



All experiments indicate that acclimatization to extreme tem- 

 peratures is accompanied by a rise of the optimum. Thus Men- 

 delssohn placed Paramecia in a trough whose temperature was 

 24-28 at one end and 36-38 at the other. They all col- 

 lected at the cooler end. The whole trough was then heated to 

 36-38 for from four to six hours. When the temperatures were 

 again brought to 24-28 at one end and 36-38 at the other, 

 they all collected at the warmer end. 1 This experiment is akin 

 to that of placing one hand in cold water and the other in hot 

 for a few seconds, and afterwards plunging them both into the 

 same dish. Whatever the temperature of this water, it will 

 seem warm to one hand and cold to the other. It is supposed 

 that increased resistance to heat is accompanied by loss of 

 water in the protoplasm. 



Acclimatization to cold. It is matter of common experience 

 that both man and the domestic animals become accustomed to 

 the cold of winter as they do to the heat of summer, and endure 

 without distress temperatures that, if suddenly imposed, would 

 prove most uncomfortable. Certain species have become so 

 attuned to cold as to live and multiply in extremely low temper- 

 atures. Such are the several species of Protista that give rise 

 to the " red snow" of the arctics, the " glacier flea" (Desoria 

 glacialis) living on the Swiss glaciers, and other species that 

 thrive where the temperature is below the freezing point of 

 water. Swarmspores are exceedingly sensitive to cold, yet 

 " Strasburger cites a case of a marine alga in which they were 

 being formed and thrown out when the temperature of the water 

 was between 1.5 and 1.8 C." 2 



All this shows that the temperatures at which protoplasm is 

 active are in large measure dependent on the temperatures at 

 which the organism is forced to live. 



Acclimatization to light. There are some indications of a 

 constitutional " attunement " to light, which may be altered by 

 exposure to changed intensity, but the matter is not well worked 

 out, and more data are required before definite conclusions can 

 be drawn. 



1 C. B. Davenport, Experimental Morphology, Part I, p. 254. 



2 Ibid. p. 257. 



