Temperatures of Reptiles, etc. 67 



seen in the mammals, but more still in the birds. But this warm- 

 blooded active condition was produced by no sudden emergence ; 

 the monotremes and marsupials form a gentle gradation between 

 the reptile and the carnivore or ungulate ; while, so far as 

 indications point, there is reason to believe that the lower birds 

 still are reminiscent of a once existent chain of links which 

 equally joined the cold-blooded lizards to those warmest-blooded 

 of all creatures, the passeriformes and fringilliformes. 



