The bottom of the ocean, we were assured, was a region of eternal darkness and of frightful pressure, wherein no living creatures could exist.

Yet the first dip of the deep-sea trawl brought up animals of marvelous delicacy of organization, which, although curiously and wonderfully adapted to live in a compressed liquid, collapsed when lifted into a lighter medium, and which, despite the assumed perpetual darkness of their profound abode, were adorned with variegated colors and furnished with organs of phosphorescence whereby they could create for themselves all the light they needed.
Even the fixed animals of the sea, growing, like plants, fast to the rocks, are frequently vivid with living light, and there is a splendid suggestion of nature's powers of adaptation, which may not be entirely inapplicable to the problems of life on strange planets, in Alexander Agassiz's statement that species of sea animals, living below the depths to which sunlight penetrates, "may dwell in total darkness and be illuminated at times merely by the movements of abyssal fishes through the forests of phosphorescent alcyonarians." In attempting to judge the habitability of a planet such as Venus we must first, as far as possible, generalize the conditions that govern life and restrict its boundaries.
On the earth we find animated existence confined to the surface of the crust of the globe, to the lower and denser strata of the atmosphere, and to the film of water that constitutes the oceans.

It does not exist in the heart of the rocks forming the body of the planet nor in the void of space surrounding it outside the atmosphere.

As the earth condensed from the original nebula, and cooled and solidified, a certain quantity of matter remained at its surface in the form of free gases and unstable compounds, and, within the narrow precincts where these things were, lying like a thin shell between the huge inert globe of permanently combined elements below, and the equally unchanging realm of the ether above, life, a phenomenon depending upon ceaseless changes, combinations and recombinations of chemical elements in unstable and temporary union, made its appearance, and there only we find it at the present time.
It is because air and water furnish the means for the continual transformations by which the bodies of animals and plants are built up and afterward disintegrated and dispersed, that we are compelled to regard their presence as prerequisites to the existence, on any planet, of life in any of the forms in which we are acquainted with it.

But if we perceive that another world has an atmosphere, and that there is water vapor in its atmosphere--both of which conditions are fulfilled by Venus--and if we find that that world is bathed in the same sunshine that stimulates the living forces of our planet, even though its quantity or intensity may be different, then it would seem that we are justified in averring that the burden of proof rests upon those who would deny the capability of such a world to support inhabitants.
The generally accepted hypothesis of the origin of the solar system leads us to believe that Venus has experienced the same process of evolution as that which brought the earth into its present condition, and we may fairly argue that upon the rocky shell of Venus exists a region where chemical combinations and recombinations like those on the surface of the earth are taking place.