296 ORDER AND SUCCESSION OF LIFE. 



matured, and the plant or animal gives "birth to similar 

 plants and animals, and the course of reproduction may 

 endure for ages. Wherever heat, light, and moisture are 

 present, there life occurs, fitted partly for the air, partly for 

 the land, partly for the waters, and partly also for a para- 

 sitic existence, on and within the tissues of other plants 

 and animals. Unless under the extremes of heat and cold, 

 life is everywhere present, restricted, no doubt, to a thin 

 film of the globe measuring vertically, but spreading hori- 

 zontally over every belt of latitude, and enjoying, each 

 order according to its grade of organisation, the realisations 

 of growth and reproduction. We can imagine a material 

 world devoid of all manifestations of life, and such our 

 planet may have been during ages of which we have no geo- 

 logical indication ; but, constituted as it now is, its harmo- 

 nies would be incomplete without the presence both of 

 vegetable and animal existences. Not only is the presence 

 of the one necessary to the life of the other, but both are 

 indispensable to the consumption and reproduction of those 

 substances by which the structure and individuality of our 

 globe is maintained. The crust of our earth is a thing of 

 vegetable and animal as well as of mineral growth, and we 

 may be assured, that from the beginning it was contem- 

 plated that each should perform its part in the harmonious 

 maintenance of the whole. The mineral building up its 

 chemically composite structure, the plant disintegrating and 

 living upon these elements, the herbivorous animal feeding 

 upon the plant, the carnivorous animal upon the herbivor- 

 ous, the animal breathing the oxygen of the atmosphere and 

 exhaling carbonic acid, and the vegetable imbibing carbonic 

 acid and discharging in turn the oxygen, are but so many 

 stages in a cosmical succession as harmonious in its adjust- 

 ments as it seems interminable in its duration. Mineral, 

 vegetable, and animal, are evident co-adaptations of the 



