84:8 TEMPERATURE OF ^:CHiD^~A ACULEATA, 



and tliis is the most probable afteinoon-leinperature of Echidna 

 (hiring the pcnod in question. I'he line B' joins the air-teniper- 

 atiires corresponding to the diii'crent temperatures of Echidna, 

 and is indicated by dots. 



Curve C, Text-fig. 2, is the ogive of the morning-temperatures 

 of Echidna during the spring sunnner period. C is the corres- 

 ponding fre([uency-curve. Its maximum lies at .'^OO C, and this 

 is the most piobable morning-temperature of Echidna during 

 spring and summer. The line 0" joins the average air-temper- 

 atiu'es as before, and is indicated by circles. 



Curve D, Text-fig. 2, is the (jgive of the afternoon-temperatures 

 of Echidna during the spring-sunnner period. D' is the corres- 

 })onding frequency-curve. The curve, it will be noticed, does 

 not fall after rising to its maximum, but remains constant. The 

 maximal value is reached at a temperature of 32 6°C. Above 

 this temperature the frequency-curve is horizontal, and tlie tem- 

 perature of Echidna varies at random. These facts indicate that 

 there is an upper, as well as a lowei-, limit of temperature beyond 

 which the temperature-regulating mechanism breaks down, and 

 Echidna behaves as a poikilothermal animal. This mechanism 

 is only etfective while the animal's body-temperature lies between 

 about 27 "6 C. and -Vi'G'C, that is, over a range of variation of 

 about 5 C. 



The line D' joins the average air-temperatures corresponding 

 to the dili'erent aftei'noon-tcm}»eratures of Echidna during the 

 spring-summer period. 



The four curves show, that most probable temperatures of 

 Echidna are 2*6'C. lower in tlie morning than in the afternoon 

 during both of the periods in which the observations were 

 made. 



The most }n-obal)le temperatures of the spring-summer period 

 were very slightly (0'3'C.) higher than the corresponding tem- 

 peratures of the autumn-winter period. The average air-temper- 

 atures were about 5"C. higher in the former than in the latter 

 period. 



