NATURAL HISTORY OF CREATION. 153 



heart of the reptiles tribes ; lastly, the ventricle being 

 also subdivided, it becomes a full mammal heart. 



It is certainly very remarkable that, corresponding 

 generally to these progressive forms in the development 

 of individuals, has been the succession of animal forms in 

 the course of time. Our earth, as we have seen, bore 

 crinoidea before it bore the higher echinodermata. It 

 presented Crustacea before it bore tislies, and when fishes 

 came, the first forms were those ganoidal and placoidal 

 types which correspond with the early foetal condition 

 of higher orders. Afterwards there were reptiles, then 

 mammifers, and finally, as we know, came man. The 

 tendency of all these illustrations is to make us look to 

 development as the principle which has been immediately 

 concerned in the peopling of this globe, a process extend- 

 ing over a vast space of time, but which is nevertheless 

 connected in character with the briefer process by which 

 an individual being is evoked from a simple germ. What 

 mystery is there here — and how shall I proceed to 

 enunciate the conception which I have ventured to form 

 of what may prove to be its proper solution ! It is an 

 idea by no means calculated to impress by its greatness, 

 or to puzzle by its profoundness. It is an idea more 

 marked by simplicity than perhaps any other of those 

 which have explained the great secrets of nature. But in 

 this lies, perhaps, one of its strongest claims to our faith. 



The whole train of animated beings, from the simplest 

 and oldest, up to the highest and most recent, are, then, 

 to be regarded as a series of advances of the principle, of 

 development, which, have depended upon external physical 

 circumstances, to which the resulting animals are appro- 

 priate. I contemplate the whole phenomena as having 

 been in the first place arranged in the counsels of Divine 



