EVOLUTION 503 
plication has been two-fold: (i) simple individuals, 
whether mountains, rivers, planets, animals, or plants, have 
become more complex (e.g., compare the structure of 
Pleurococcus, a simple spherical cell, with that of the fern) ; 
(2) the relation between living things, and between them 
and their surroundings has become more complex (e.g., 
compare a unicellular bacterium, with its relatively simple 
life relations, with the clover plant, highly organized, 
and related to water, air, soil, light, temperature, gravity, 
bacteria (in its roots), and insects (for cross-pollination). 
Most of the steps of evolution have been progressive, 
toward higher organization, greater perfection of parts, 
increased efficiency of function, as, for example, from algae 
to angiosperms; but not all the steps have been in 
this direction. Some of the steps have been regressive, 
toward simpler organization, less perfection of parts, 
decreased efficiency of function, as, for example, from 
green algae to the alga-like fungi (Phycomycetes), from 
independence to parasitism (dodder), or to saprophytism 
(Indian pipe and bread-mold) . 
436. Inorganic Evolution. The process of evolution is 
not confined to living things, but, as indicated above, 
applies to all nature. Even the chemical elements are 
now believed to have been produced by evolutionary 
changes, and to be even now in process of evolution. This 
is one of the results of the recently discovered phenomenon 
of radioactivity, which is essentially the transformation 
of the atoms of one chemical element into those of another. 
Fossil remains of marine animals and plants, found im- 
bedded in the rocks on mountain summits, indicate, 
without possibility of reasonable doubt, that what is now 
mountain top was formerly ocean bottom. The mountain 
