THE STUDY OF BIOLOGY. 35 



The theory thus presented, calls to its aid all the facts of biological 

 science. It shows by development, that the way of nature is that of 

 progressing from the general to the special. It notes that extinct 

 forms of life can frequently be shown to be intermediate between 

 living forms, and that "missing links" are capable of being supplied 

 as knowledge grows and as research advances. It correlates out- 

 ward or physical changes in land and sea with the change in species, 

 and shows how varying conditions of life modify the living form. It 

 enlists, as we have seen, the facts of geographical distribution in its 

 favour, and proves, by an appeal to geology as well, that the modifi- 

 cation of life through the changes of land and sea accounts for the 

 otherwise puzzling phenomena viewed in the distribution of living 

 beings over the world's surface. Laying hold of every detail of 

 natural science, this theory of nature has thus wrought a mighty 

 revolution in biology ; whilst geology and other sciences have 

 moulded their conceptions on the consistent theory of the universe 

 which evolution lays down. It is the pride and boast of evolution 

 that the avenues to which knowledge leads through this theory of 

 the universe are illimitable that knowledge may truly " grow from 

 more to more " under its benign influence. And, best of all, whilst 

 science is thus made the handmaid of truth, we also find that the 

 spirit of reverence in face of the facts of nature is also inculcated 

 by the study of development. There is no room for the idea of 

 arbitrary interference with the laws of nature when evolution has 

 fairly asserted its right to be heard. As in the inorganic world 

 around us law reigns supreme, as planets revolve in their cycles 

 with unchanging regularity, so in the world of life there is demon- 

 strated to us the existence of law and ordered sequence which 

 prevails in lowest as in highest spheres of being, which directs the 

 destinies and development of man equally with the movements of 

 the animalcule, and which as fully explains the evolution of a leaf, 

 as it does the formation of a world. 



