THE PHYSIOLOGICAL EVOLUTION, ETC. 



385 



only produce such a considerable elevation of temperature 

 when large numbers of them are confined in a small space. 

 A single bee exposed to a low temperature soon becomes 

 torpid and almost motionless. 



We now come to the very interesting observations 

 which have been recently made upon the temperatures of 

 monotremes and marsupials. Upon the duck-billed platy- 

 pus [Ornithorhyncus paradoxus), which is the lowest of the 

 monotremes, and in fact the lowest member of the whole 

 class of mammals, two observations, both on the same in- 

 dividual, have been made by Miklouho-Maclay. 1 As a 

 mean, the temperature was found to be 24*8°, or only 2 '6° 

 higher than that of the water in which the animal was kept. 

 It would therefore seem to be more closely related to the 

 cold- than to the warm-blooded animals. The same ob- 

 server also made several observations 2 upon another mono- 

 treme, Echidna hystrix. The mean temperature was 28*0°, 

 that of the air being 20*0°. Semon 3 also made several de- 

 terminations, and found the average rectal temperature to 

 be 32*5°. Sutherland 4 has recently investigated the subject 

 more fully, and has determined how the temperature of the 

 animal is affected by that of its surroundings. The follow- 

 ing are the means of the results obtained by him : — 



Here we see that the temperature of these animals is 

 affected very considerably by that of the environment, and 

 that by increasing the temperature from 14* i° to 45 'o°, the 

 mean temperature of the animals rose from 257 to 36 '6°. 

 Even these figures do not express the extreme temperature 



1 Proc. Linn. Soc. N. S. Wales, ix., p. 1204. 

 3 Arch./, d. ges. Physiol., Bd. 58, S. 229, 1894. 



2 Ibid., viii., p. 425. 

 4 Ibid. 



