376 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
marine to terrestrial, nonvascular to vascular, invertebrate to verte- 
brate, fish to mammal, marsupial to man. This is not all. We would 
read how, as old forms died out and new ones came on, there arose, 
both in plants and animals, not only more effective relations to en- 
vironment, but more elaborate mechanisms whereby the parent as- 
sured the safety of the young. 
We would see too an increasing interdependence among living 
things, and between them and their physical surroundings. The fos- 
sil hunters of today are not content merely to describe single species. 
They go beyond this to identify social groups of extinct plants and 
animals. Yet in spite of this increasing fitness of living organisms 
we read no evidence in the record that any form of life ever had 
things completely its own way. All were subject to some great prin- 
ciple of give and take, leading toward a balance or equilibrium. 
And finally if we took account of sediments and earth forms, of 
the chemistry and geometry of rocks, we would find clear evidence 
that living organisms have played an increasing part in geological 
processes as time has gone on. We should see how the exclusively 
physical processes of erosion, deposition, and crustal readjustments 
came to be supplemented by organic sedimentation, the stabilization 
of land forms by vegetation, and the modification of the flow of 
energy and interchange of materials by many activities of plants 
and animals. 
Since such interrelationships between life and environment are 
the peculiar business of ecology, a few words on that branch of bio- 
logical study are in order. In 1959 we shall celebrate the centennial 
of a landmark in man’s intellectual progress—the publication of Dar- 
win’s “Origin of Species by Natural Selection.” You will recall that 
the problem to which Darwin had addressed himself many years 
earlier was that of trying to account for the bewildering variety and 
astonishing fitness of living organisms, both plants and animals. 
Some measure of this task may be had if we recall that perhaps 
300,000 species of plants and nearly a million of animals have been 
identified. 
Darwin had at hand two powerful intellectual tools, one borrowed 
from geology, the other from political economy. The first was the 
principle of uniformity, which assumed that in nature events of the 
past have been determined by those forces that we see in operation 
today. The second was the idea that living beings have a far greater 
capacity to reproduce than to survive. Somehow their numbers, 
through the generations, are kept in balance with the space and means 
of subsistence available. Many are born that do not mature, or if 
you prefer to be Scriptural, many are called but few are chosen. 
Fortunately Darwin was a naturalist, trained to observe nature in 
all her aspects. He noted, although he could not explain, the tend- 
