230 EVOLUTION, OLD AND NEW. 



since the earth began to exist, perhaps millioas of ages 

 before the commencement of the history of mankind 

 — would it be too bold to imagine that all warm-blooded 

 animals have arisen fcom one living filament, which 

 the Great First Cause endued with animality, with the 

 power of attaining new parts, attended with new pro- 

 pensities, directed by irritations, sensations, volitions, 

 and associations; and thus possessing the faculty of 

 continuing to improve, by its own inherent activity, and 

 of delivering down those improvements by generation 

 to its posterity world without end ! 



" Sixthly, the cold-blooded animals, as the fish tribes, 

 which are furnished with but one ventricle of the heart, 

 and with gills instead of lungs, and with fins instead of 

 feet or wings, bear a great similarity to each other ; 

 but they differ nevertheless so much in their general 

 structure from the warm-blooded animals, that it may 

 not seem probable at first view that the same living 

 filament could have given origin to this kingdom of 

 animals, as to the former. Yet are there some creatures 

 which unite or partake of both these orders of anima- 

 tion, as the whales and seals ; and more particularly 

 the frog, who changes from an aquatic animal furnished 

 with gills to an aerial one furnished with lungs. 



" The numerous tribes of insects without wings, from 

 the spider to the scorpion, from the flea to the lobster ; 

 or with wings, from the gnat or the ant to the wasp and 

 the dragon-fly, difier so totally from each other, and 

 from the red-blooded classes above described, both in 

 the forms of their bodies and in their modes of life ; 

 besides the organ of sense, which they seem to possess 



