Thermal adjustment and respiratory exchange in monotremes and mersupials.—A study in the development of homothermism

A number of observations on the relations between the body temperature, and the temperature of the surrounding medium, and on the respiratory exchanges in monotremes and marsupials are recorded. The results are compared with those obtained in control experiments with cold-blooded animals (lizards) and higher mammals. The main conclusions arrived at are— 1. Echidna is the lowest in the scale of warm-blooded animals. Its attempts at homothermism fail to the extent of 10° when the environment varies from 5° to 35° C.