§4] ACCLIMATIZATION TO EXTREME TEMPERATURES 251 



To summarize : Protista are stated to have been found in 

 nature in water at temperatures far above 60° C. The most 

 striking cases are of Oscillaria and " Conferva " from several 

 localities, which resist nearly up to the boiling point of water. 

 The closely allied Nostocs are, perhaps, next most abundant 

 and resistant, reaching 93° (possibly Protococcus) in the Cali- 

 fornia geysers. Metazoa are stated to live at temperatures 

 far above 45°. Although some doubt has been cast on No. 22 

 by Hoppe-Seylbr's inability to confirm Eheenberg's observa- 

 tions, the case seems established of Cypris thriving at 45° to 

 50.5°. Very extraordinary are the observations Nos. 24 and 

 25 on Stratiomys larvee, which, however, are sadly in need of 

 confirmation by competent observers. Leaving out of account, 

 for the moment, the less well established cases, there still 

 remains abundant evidence that organisms can live and thrive 



