214 SECRETS OF ANIMAL LIFE 
inquire how the callous, rough-and-tumble condi- 
tions of the outer world allowed of the germination 
and growth of that tender plant which we call life. 
In this inquiry we shall chiefly follow the con- 
siderations recently brought forward by Professor 
Chamberlin in his Origin of the Earth (Chicago 
University Press, 1916), and by Professor Hender- 
son in his Order of Nature (Harvard University 
Press, 1917). 
Around the young earth, more or less cooled 
down, there was wrapped an atmosphere, laden with 
“ planetesimal”’ dust which sank gently on to the 
surface and drifted about in billowy, changeful 
dunes. By its early “ultra-Krakatoan”’ atmo- 
sphere, as Professor Chamberlin calls it, “ the 
young earth was blanketed against intensities of 
radiance from without” (a younger, more intensely 
radiant sun) “and inequalities of radiance from 
within.” This “preparation” afforded by the 
atmosphere was probably of great importance, 
for the average living creature, as we know it, is 
adapted to mild temperatures and gentle reactions 
and ill suited for violent vicissitudes. Time passed, 
and from the growing atmosphere water condensed 
on the surface of the earth, and was gradually 
absorbed by the porous, dusty mantle, till by and 
by in the hollows among the dunes there appeared 
pools and lakelets, from which grew lakes and seas. 
To an atmosphere was added a second “prepara- 
tion,” a hydrosphere, and that brought the possi- 
ebility of life nearer. 
