NOTES TO TABLE XXI 263 



either the beginning of coagulation (maximum) or the cessa- 

 tion of chemical change (minimum) appears. Finally, death 

 takes place at the ultramaximum through coagulation of the 

 proteicls, while it may occur beyond the minimum also, if the 

 protoplasm contains much water. The optimum temperature 

 is unlike in the different species, and certain individuals even 

 may gain a very high or low optimum (lying even beyond the 

 normal extremes) through the process of gradual acclimatiza- 

 tion. The acclimatization seems to be due to the direct action 

 of the varying environment upon the constitution of protoplasm. 

 Finally, many simple organisms (probably all protoplasm) re- 

 spond to heat by a locomotion which is adapted to keep them 

 at the temperature to which they are attuned. The movement 

 seems to be determined by the difference in intensity of heat at 

 the different parts of the body. This whole chapter reveals 

 protoplasm as a substance whose integrity is limited by chemico- 

 physical conditions. Within those limits, however, it is highly 

 sensitive to changes in temperature, becoming so altered by an 

 untoward temperature as not to be injured by it, or migrating, 

 if possible, so as 'to keep in the temperature to which it is 

 already attuned. In a word, protoplasm shows itself to be a 

 highly irritable, automatically adjustable substance. 



NOTES TO TABLE XXI (p. 250) 



1. The Chroococcus was found in some of the fronds of Nostocs from Owen's 

 Valley (see No. 3); but it is not stated whether they were in those Nostocs 

 which were derived from the hottest springs. 



2. No details are given by BREWER concerning the method of determining 

 temperature. " In these warm mineral waters low forms of vegetation occur. 

 The temperatures were carefully observed in many cases. The highest tem- 

 perature noted, in which the plants were growing, was 93 C. (about 200 F.). 

 But they were most abundant in waters of the temperature 52 to 60 (125 to 

 140 F.). In the hotter springs the plants appeared to be of the simplest kind, 

 apparently, simple cells of a bright green color ; but they were examined only 

 with a pocket lens. In the water below, about 60 to 05 C., filamentous Con- 

 fervpe formed considerable masses of a very bright green color." In a letter to 

 WYMAN, however, BREWER says, concerning the same locality and determina- 

 tions : "The temperatures given here were carefully observed with a standard 

 Centigrade thermometer, with a naked elongated bulb," and "at the higher 

 temperature [93 C.] they [the vegetable forms] were not abundant and existed 

 as grains like Nostoc or Protococcus, intensely green and rather dark." 



