EVOLUTIONARY ASPECTS IN MAMMALS 



to 1903, G. J. Martin did a very outstanding study on thermal adjust- 

 ment in monotremes and marsupials. The sub-title of his paper was 

 "A Study in the Developmentof Homeothermism."To my knowledge, 

 this is the only published study with this title ever made. Since 

 Martin, incontrastto his contemporaries, also tried to record meta- 

 bolism and parameters of physical heat exchange and behavior, I 

 prefer to postpone the discussion of his main findings until after a 

 brief review of the following work done on temperature measure- 

 ments of monotremes. In 1915, Wardlaw presented a long paper 

 entitled "The Temperature of Echidna aculeata ." He reports average 

 body temperature in the neighborhood of 30 G.Wardlaw's extensive 

 records also contain data on seasonal as well as diurnal variations in 

 body temperature. Morning temperatures would invariably be higher 

 than afternoon temperatures, the difference being about 3 C. 

 Wardlaw's data indicates a diurnal temperature change independent 

 of the external air temperature. He also indirectly comments on the 

 ability of the Echidna to increase rather rapidly its metabolism and 

 body temperature during arousal from hibernation. 



Burrell, in his monograph on the platypus (1927), reports that 

 the body temperature for seven females of this species ranged 

 between 30° C and 33 C. Wood- Jones (1923) had earlier reported 

 an average of 32.2 C for the same species. 



Martin (1903) set as his purpose locating the monotremes and 

 marsupials on the ascending scale of superiority towards freedom 

 from the environment. He recorded thebody temperature variations 

 at controlled air temperatures between 4 C and 40 C. His main 

 concern was, however, to ascertain to what extent variation in heat 

 production and variation in heat loss were used for purposes of 

 adjustment. For comparison, he used lizards, Cyclodusgigas,cats, 

 and rabbits besides the monotremes and marsupials. Figure 2 rep- 

 resents Martin's findings in regard to the relationships between 

 body temperature and air temperature. The results were recorded 

 under laboratory conditions where behavior as a means of adjust- 

 ment was drastically reduced or impaired. The Echidnas display a 

 variance of about 10 C between the extremes of air temperature. 

 Ornithorynchus displays somewhat less variance and also regulates 

 at a higher level. The marsupials studied, Dasypus maculatus , 

 Bettongia, (the kangaroo rat) and the opposum, Trichosurus 



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