HAECKEL: HIS LIFE, WORK, AND COMPANIONS 81 
though in the days of Linnzeus those known were hardly a 
twelfth of that number. 
To many studious men the species of Linnzeus repre- 
sented typical forms of life brought into being by creative 
fiat ; forms of life capable of reproducing offspring in con- 
tinuous succession, which, like themselves, would remain 
separate, distinct, immutable, without variation beyond 
narrow limits. But to those holding such a theory, the 
remains of fossil extinct organisms seemed anomalous. 
Moreover among those extinct fossils were strange gigantic 
creatures. In America the megather1tum was found ; the 
mammoth was found on the coast of Siberia; and in 
England icthyosauria were found. Numerous explanations 
regarding the extinction of these monsters were given. Sir 
Anthony Carlisle, a great surgeon in his day, thought they 
were just sent down from heaven to see whether earth 
would support them. A more thoughtful explanation was 
that before the flora and fauna known to man, there were 
long periods of tranquility in the earth’s history, each 
period having its own plants and animals, and each period 
being followed by a catastrophy annihilating one set of 
organic beings, and ushering in a newcreation. ‘This was 
the widely accepted theory of cataclysms, favoured to some 
degree by no less an authority than Cuvier. But early in 
1830 appeared the first volume of Lyell’s ‘‘ Principles of 
Geology,’’ a work destined to be a landmark in the history 
of science. It was from the first recognized as a dispassion- 
ate, well reasoned refutation of the catastrophic school of 
geologists, and a lucid exposition of the doctrine that the 
geological history of the earth has run a course of uniform 
continuous development in conformity with laws like those 
now in operation. 
When, in 1831, Darwin, as naturalist on the Beagle, 
embarked for South America on a scientific expedition, he 
took with him Lyell’s newly published volume. And in 
part from Lyell’s reasoning, and in greater part from his 
