EFFECT OF CHANGES OF TE3IPERATVRE. 331 



He made for nearly ten years observations on tlie lower 

 Infusoria when subjected to change of temperature. 

 Having patiently studied the lifo-histoiies of a number of 

 species of monads, he determined to watch their behavior 

 under a gradual increase of temperature, and although, in 

 the low forms he observed, a new generation comes into 

 existence every four minutes or so, it took years of experi- 

 mentation to raise the temperature to 158° F. Beginnini; 

 the normal temperature of C0° F., in four months it was 

 raised to 70°, without, however, affecting the monads, 

 which continued to multiply by fission as vigorously as 

 before. When a temperature of 73° was reached, however, 

 an adverse influence seemed to be exerted on the organisms 

 as regards their vitality and productiveness; but by keeping 

 the temperature constant for two months the new gener- 

 ations became, so to speak, acclimatized, and in five 

 months more the temperature was gradually raised to 78°. 

 These experiments were continued until the temperature 

 of 158° F. was reached, when an accident put an end to the 

 experiments. 



With littlo doubt the cold of the glacial period caused a 

 widespread extinction of life at the end of the Tertiary 

 Period; a few forms adapted themselves to a minimum and 

 survived, forming the arctic fauna and flora. 



Effects of Change of Climate. — When animals are trans- 

 ported from one region or one country to another, they 

 undergo more or less marked changes, due to difference in 

 moisture or dryness, altitude, soil, etc. The following 

 facts bear on this subject: Babbits which have been taken 

 to the Pic du Midi Observatory (9500 feet above the sea- 

 level) have produced in seven years a race somewhat differ- 

 ent from their original race in the surrounding plains. 

 They are a little smaller, have less developed ears, and their 

 fur coats are of a lighter color and very thick. Moreover, 

 the consistence of their blood has undergone a notable 

 change. It contains more iron, and possesses a greater 

 power of absorption for oxygen. The writer goes on to say 



