Art. VIII. — The Temperatures of Reptiles, MonotreTnes 

 and Marsupials. 



(Plate VI.). 



By Alexander Sutherland. 



[Read 4th June, 1S9G.] 



There has for many years past been a tendency to tl'minish or 

 ignore the distinction between the cold-blooded and the warm- 

 blooded types of animal life. Quite a number of writers adopt 

 the habit of speaking of " the so-called cold-blooded animals," as 

 if the contrast were an unfounded belief that increasing know- 

 ledge is fast abolishing. Yet the difference is one that is not 

 only real, but in some respects radical. In very few, however, of 

 nature's classes is there found a line of sharp demarcation, and 

 the chief purpose of this paper is to point out that, though the 

 distinction between the two types is real, there lies between these 

 two types a line of steady gradation. 



Although the invertebrates have the capacity of producing 

 heat, they are themselves cold-blooded. With the exception of 

 the insects, they very rarely rise more than a fraction of a degree 

 above the temperature of the media in which they happen to be. 

 According to observations of Professor Valentin, polypi, medusa?, 

 echinoderms, molluscs, crustaceans and cephalopods are able to 

 raise themselves about a fifth of a degree, sometimes as much as 

 three-fifths of a degree, above their environment.* 



Among insects the power of heat-production is very much 

 greater. Though essentially cold-blooded creatures, in the sense 

 that they have no fixed standard of body-heat towards which 

 they approximate, they are almost always warmer than their 

 media; but if they are at rest that excess is only a degree or two. 

 In case, however, of severe exertion, they are capable of warming 

 themselves to a remarkable extent. George Newport showed 

 that an ants', bees', or wasps' nest at a period when its inmates 

 are dormant will not be more than a tenth of a degree warmer 

 than the surrounding air. But when the insects are roused and 

 excited they are able, by rapid movements of their wings, to warm 



" AH Degrees in this paper are Centigrade. 



