and (3) lifeless earth was \'isited by ~xtraterrestrials who either
deliberately or accidentally left microbes behind when they departed.
Variations of and objections to hypothesis are given.
Calvin, Melvin. Chemical evolution. In Cameron, A. G. W., ed.
Interstellar communication. New York, W. A. Benjamin, 1963.
p. 33-77.
From questions on the nature and characterist!cs of life, the author proceeds
to hypotheses on chemical evolution and the establishment of an environment
conducive to the origin of sell-replicating macromo!ecules. Specul:ltiun on
life on oth.1r planets, life elsewhere in the solar system, and life in the ga-
lactic systems is followed by a discussion of man's place in the universe. Of
the two hundre.1 million inhabitable planets in the visible universe, two areas
selected for attempt at interstellar communication (PNject Ozma) are Tau
Ceti and Epsilon Eridani. Reasons are given for their selection.
Calvin, Melvin. Origin of life on earth and elsewhere. Annals of internal
medicine, v. 54, May 1961: 954-976.
Traces chemical evolution to the poi11t wha-e a primitive organism is
formed. Applies this reasor.i.ng to question of wheth{!r we are likely to
find that similar events have occurred elsewhere than on earth.
Firsoff, V. Axel. Life, mind and galaxies. Edinburgh and London, Oliver
& Boyd, 1967. 111 p.
Evidence is presented to show that life is not a freak occurrence in the
universe of stars and nebulae, but an integral part of its general pattern,
and will arise naturally from the inorganic substratum wherever and when-
ever conditions become suitable for it, and, that these may be suitable for
life of a different chemical order even though unfit for our type of carbo-
hydrate biology. It is postulated that no definite boundary can be fixed
between the organic and the inorganic world, which shade into each other
by imperceptible debrees.
Gatland, Kenneth W. and Derek D. Dempster. The inhabited universe.
London, Alan Wingate, 1957. 182 p.
The theme throughout the book is that evolution is constantly brin~i:-c: new
forms of life into existence an<.l that creation is a continuous process. Man
is depicted as the product, not merely of a limited biological development,
but of an i11herent facet of cosmic evolutior..
Huang, t1u-Shu. Occurrence of life in the universe. American scientist,
v. 47, September 1959: 397-402.
Prerequisites for the occurrence of life, especially in an advanced form,
are discussed in the light of current knowledge of the stars and their
evolution.
225