62 Proceedings of the Royal Society of Victoria. 



38-9", as calculated from Dr. John Davy's lists (Edin. Phil. Journ. 

 1825, p. 300), while the average of a similar but shorter list 

 supplied by Max Fiirbinger is 39°. We may take this as fairly 

 indicative of the general mammal temperature, which does not, 

 except in constitutional disturbances, vary so much as two degrees 

 on either side of this limit. No mammal indeed seems in good 

 health to be warmer than 40° ; scarcely any descend lower than 

 37°. 



The platypus, therefore, at only 24*8 J is almost a cold-blooded 

 animal. The only other genus of monotremes, the echidna, 

 carries us a step upwards. Baron Miklouho-Maclay's average of 

 live observations is 28°, while the air was 20°. I have kept at 

 different times fourteen specimens of Echidna hystrix and made 

 twenty-seven observations on the temperatures of all I happened 

 to have at any particular time. I found the average to be 

 29 - -T, or nearly a degree and a half above that of the Baron. 

 But these animals show their affinity with the reptiles by a 

 temperature so variable with the weather that we may readily 

 expect the average of one series of experiments to differ very 

 considerably from that of another. 



An echidna one cold morning was so low as 22° ; another, 

 brought in from the forest in a sack exposed to a tierce midday 

 heat, registered so high as 36 - 6 J . The following table will 

 represent the general character of the variations, the temperatures 

 in each case being the average of from three to six individuals, 

 which never varied from one another at the same time more than 

 a fifth of a degree : — 



