68 



NA rURE 



[November i8, 1897 



may take this as fairly indicative (if the general mammal temper- 

 ature, 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 is almost a cold-blooded 

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

 carries us a step upward^. Baron Miklouho-Maclay's average 

 of five observations is 28", while the air was 20°. I have kept at 

 different times fourteen specimens oi 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°"4, 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 as low as 22° ; another, 

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

 heat, registered as high as 36^ 6. The accompanying diagram 

 (Fig. 2) represents the general character of the variations, the 

 temperatures in each case being the average of from three to six 

 individuals, which never vary from one another at the same time 

 more than a fifth of a degree. 



It will be seen that the temperatures of the echidnre varied 

 from 22° to 36° '6. This is an immense range for a mammal, 

 and suggests a reptilian want of capacity for temperature regu- 

 lation. Moreover, though the concomitancy between the air 



to 36° '4. Females at the breeding time are always very 

 decidedly above the ordinary degree of warmth. If such cases 

 be excluded, the average is exactly 36°. But the average for 

 males alone is only 35^*2. The range of variation may be seen 

 in Fig. 3. 



The range is not very wide, yet I have often known healthy 

 specimens that had been for a while in the sun stand as high as 

 37° -9, while on a cool day or in a: very shady place the same 

 individuals would be only 35° '3, a range greater than we would 

 find under the same circumstances in any of the higher mammals. 

 The highest register I ever obtained for a thoroughly healthy 

 koala was 38° '4, which is a degree and a half above the normal 

 temperature of man ; the lowest was 34° '9, or nearly two degrees 

 below man's normal. 



According to observations taken for me by Mr. Ernest Le 

 Souef, the Dasyures come next at an average of 36''. 



Phalangers stand next in order. The average of twenty- two 

 observations on from two to four specimens of the ring-tailed 

 opossums (Phalangista) gave 36° 6, which is only a little below 

 the normal human temperature. But again the range was much 

 greater than one finds in any of the higher mammals. In cool 

 weather, with the thermometer at 16 '8, a male would register 

 about 35°, a female about one-tenth of a degree higher ; but in 

 warmer weather, though still in -the shade, where the thermo- 

 meter registered 31° to 35°, the opossums would be about 37°. 



Mr. Ernest Le Souef took for me the temperatures of three of 

 these Australian opossums in the Melbourne Zoological Gardens. 

 Phalangista viilpina gave "ifi^'i, Phalangista fuliginosa 37° ■3. 



Fig. 2.— To s.iow want of concomitance in the temper.itures of Echidna 

 and air. Upper line. Echidna ; lower line, air. 



and the body temperatures is by no means strict, there is enough 

 to show that the one in a large measure follows the other. It 

 is to be remembered that while a monotreme may rise and fall 

 with the air, yet the one change will follow the other after a 

 definite period of time, and an hour after sunset, though the air 

 in a box may have grown much cooler, the echidnae in that box 

 may have only begun to cool. 



The next stage in the anatomical classification brings us into 

 the order of the marsupials, and here again we make an upward 

 step in view of a temperature higher, but not so high as that of 

 mammals in general ; steadier, but not so steady as is usual in 

 all the remaining orders. I have observed the temperatures of 

 sixteen different species of marsupials, and they average 36° 

 exactly, as the result of 126 observations. They are thus 3° below 

 the average of other mammals. 



The marsupial whose temperature, so far as I have observed, 

 comes next above the monotremes is the wombat, which stands 

 at 34° "I, as the average of single observations made on two 

 specimens [Phascoloinys lasiorhiniis, 34° '3, and P. platyrhinus, 

 34°). Next seems to stand the genus Petaurus, or flying squirrel. 

 Mr. Ernest Le Souef was good enough to observe for me the 

 temperatures of five specimens in the Zoological Gardens of 

 Melbourne. The average is 35° 7. 



After that comes the genus Phascolarctos, our little native 

 bears or koalas. I have kept numerous specimens of this animal 

 [P. t7>/^/7/j) on his native gum trees, with nothing artificial about' 

 him save a strap and rope whereby he could be pulled down 

 from time to liuie to have his temperature observed. Thus I 

 made eighty-three observations, the average of which amounts 



NO. 1464, VOL. 57] 



YiG. -. — To show want of concomitance in the leniperaiures of Koala and 

 air. Upper line, Koala ; lower line, air. 



This corresponds with Selenka's observations of the true 

 opossums (Didelphys), which ranged about 37°. 



I have made only four observations on the temperatures of the 

 kangaroo family. They are a little under the human standard. 

 Macroptts giganteus gave 36° '6, HalmatKrtis bennettii gave 

 37°'i, Petrogale xanthopus 35°'9, while the tree kangaroo 

 {Dendrogaliis grayi) was exactly at the human standard, 37°. 



From the few recorded temperatures of rodents and in- 

 sectivores, I should think it most probable that they came next 

 in order, with perhaps the Cetacea and Sirenia, judging from 

 occasional records, as almost on the same level. All the other 

 orders of mammalia stand uniformly much above the human 

 temperature. 



It is clear, therefore, that there are grades of temperature, and 

 that the mammals which are classed lowest on anatomical 

 grounds are not only of the lowest temperature, but also of the 

 greatest range, and they are likewise, of all mammals, those 

 which are under the strongest and most direct influence of the 

 temperature of the environment. 



Similar, though much less complete connecting links may be 

 seen in the case of birds. The lowest of birds are the Ratitae, 

 or Cursores, and these appear to have the lowest temperature. 

 Mr. Ernest Le Souef took for me in the Melbourne Zoological 

 Gardens observations on the temperature of the emu. These are 

 the lowest records of bird temperatures of which I know. They 

 averaged 39° '5, while all the birds above the Ratitae are in- 

 variably over 40°. The temperature of thirty-six fowls, taken 

 quietly by night from their perches, averaged 41° exactly, while 

 that of twelve, lifted from the nests in which they were broodin j, 



