BY H. S. HALCRO WARDLAAV. 847 



frequencies of occurrence of the vari<ju8 temperatures are pro- 

 }»orlional to the ordinates. Autunni and winter temperatures 

 are given in Text-fig. 1; spring and summer temperatures are 

 given in Text-fig. 2. The morning and aftei-noon temperatures 

 are plotted separately in each diagram. The mean air-temper- 

 atures, corresponding to each range of I'C. of the animal's tem- 

 peratures, are also shown. The mnnhers of results represented 

 by each of the four pairs of curves aie as follows; autumn-winter 

 period, morning, 188, afternoon, 242 ; spring-sununer period, 

 morning, 98, afternoon, 102. Ah these numbers are different, 

 the ordinates of the different curves are not directly comparable 

 with each other. This does not matter, however, as only the 

 different ordinates of the same curve require to be compared. 



Curve A, Text-fig. 1, shows the ogive of the morning temper- 

 atures of Echidna during the autumn-winter period. Each 

 ordinate is proportional to the number of observations occurring 

 at and below the corresponding temperature. Curve A' is the 

 derived or frequency-curve; each ordinate is proportional to the 

 number of observations occurring at the corresponding temper- 

 ature. It will be seen that the maximum of this frequency-curve 

 lies at 29'7 C; this is the most probable morning-temperature of 

 Echidna during the autunni-winter period. It will also be noticed 

 that the curve A' flattens out and becomes almost horizontal 

 below a t{!m})erature of about 27 "GX'. This portion of the curve 

 continues tlown to about 8*0 C, but has not all been shown. The 

 curve indicates that, below 27'6 C, Echidna allows its tenqjer- 

 ature to vary at random, and displays no tendency to bring it 

 towards a definite value. By the time its b(xly-tenqjerature has 

 fallen to 27 '5C., Echidna has thus become a completely poikilo 

 thermal animal. 



The line A" joins the mean air-temperatures corresponding to 

 the different body- temperatures of Echidna, and is marked by 

 circles. 



Curxe B, Textlig. 1, is the ogive of the afternoon-temperatures 

 of Echidna during the autumn- winter period. Curve B' is the 

 corresponding frequency-curve. Its maximum occurs at 32*3°C., 



