320 Evolution and Adaptation 



where the temperature is very high. Thus, to give a few 

 examples, there are some of the lower plants, nostocs and 

 protococcus forms, that live in the geysers of California at a 

 temperature of 93 degrees C, or nearly that of boiling water. 

 Leptothrix is found in the Carlsbad springs, that have a tem- 

 perature of 44 to 54 degrees. Oscillaria have been found in 

 the Yellowstone Park in water between 54 and 68 degrees, 

 and in the hot springs in the Philippines at 71 degrees, and 

 on Ischia at 85 degrees, and in Iceland at 98 degrees. 



It is probable from recent observations of Setchel that 

 most of the temperatures are too high, since he finds that 

 the water at the edge of hot springs is many degrees lower 

 than that in the middle parts. 



The snail, Physa acuta, has been found in France living at 

 a temperature of 35 to 36 degrees; another snail, Paludina, 

 at Abano, Padua, at 50 degrees. Rotifers have been found at 

 Carlsbad at 45 to 54 degrees; Anguillidae at Ischia at 81 de- 

 grees; Cypris balnearia, a crustacean at Hammam-Meckhou- 

 tin, at 81 degrees ; frogs at the baths of " Pise " at 38 degrees. 



Now, there can be little doubt that these forms have had 

 ancestors that were like the other members of the group, and 

 would have been killed had they been put at once into water 

 of these high temperatures, therefore it seems highly prob- 

 able that these forms have become specially adapted to live 

 in these warm waters. It is, therefore, interesting to find that 

 it has been possible to acclimatize animals experimentally to 

 a temperature much above that which would be fatal to them 

 if subjected directly to it. Dutrochet (in 1817) found that if 

 the plant, nitella, was put into water at 27 degrees, the cur- 

 rents in the protoplasm were stopped, but soon began again. 

 If put now into water at 34 degrees they again stopped mov- 

 ing, but in a quarter of an hour began once more. If then 

 put into water at 40 degrees the currents again slowed down, 

 but began again later. 



Dallinger (in 1880) made a most remarkable series of ex- 



