FOSSIL ORGANISMS. 55 
creation,” the infallible and indisputable records which fix 
the correct history of organisms upon an irrefragable founda- 
tion. All petrified or fossil remains and impressions tell us 
of the forms and structure of such animals and plants as are 
either the progenitors and ancestors of the present living 
organisms, or they are the representatives of extinct colla- 
teral lines, which, together with the present living organisms, 
branched off from a common stem. 
These inestimable records of the history of creation 
throughout a long period played a subordinate part in 
science. Their true nature was indeed correctly understood, 
even more than five hundred years before Christ, by the 
ereat Greek philosopher, Xenophanes of Colophon, the same 
who founded the so-called Eleatic philosophy, and who was 
the first to demonstrate with convincing precision that all 
conceptions of personal gods result in more or less rude 
anthropomorphism. 
Xenophanes for the first time asserted that the fossil im- 
pressions of animals and plants were real remains of formerly 
living creatures, and that the mountains in whose rocks 
they were found must at an earlier date have stood under 
water. But although other great philosophers of antiquity, 
and among them Aristotle, also possessed this true know- 
ledge, yet throughout the illiterate Middle Ages, and even 
with some naturalists of the last century, the idea prevailed 
that petrifactions were so-called freaks of nature (lusus 
nature), or products of an unknown formative power or 
instinct of nature (nisus formativus, vis plastica). Respect- 
ing the nature of this mysterious and mystic creative 
power, the strangest ideas were formed. Some believed that 
this constructive power—the same to which they also 
