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CHAPTER VI

ON THE GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS

IN PAST AND PRESENT TIMES.

12

SECTION FIRST

Distribution of the inhabitants in the different continents-Relation of

range in genera and species-Distribution of the inhabitants in the

same continent-Insular Faunas-Alpine Floras-Cause of the simi-

larity in the floras of some distant mountains-Whether the same

species has been created more than once-On the number of species,

and of the classes to which they belong in different regions 151-174

SECOND SECTION

Geographical distribution of extinct organisms-Changes in geographical

distribution-Summary on the distribution of living and extinct

organic beings

174182

SECTION THIRD

An attempt to explain the foregoing laws of geographical distribution, on

the theory of allied species having a common descent-Improbability

of finding fossil forms intermediate between existing species 183–197

CHAPTER VII

ON THE NATURE OF THE AFFINITIES AND CLASSIFICATION

OF ORGANIC BEINGS.

Gradual appearance and disappearance of groups-What is the Natural

System –On the kind of relation between distinct groups—Classifica-
tion of Races or Varieties—Classification of Races and Species

similar--Origin of genera and families

198—213

INTRODUCTION

We know from the contents of Charles Darwin's Note Book of 1837 that he was at that time a convinced Evolutionist'. Nor can there be

Nor can there be any doubt that, when he started on board the Beagle, such opinions as he had were on the side of immutability. When therefore did the current of his thoughts begin to set in the direction of Evolution?

We have first to consider the factors that made for such a change. On his departure in 1831, Henslow gave him vol. 1. of Lyell's Principles, then just published, with the warning that he was not to believe what he read. But believe he did, and it is certain (as Huxley has forcibly pointed out') that the doctrine of uniformitarianism when applied to Biology leads of necessity to Evolution. If the extermination of a species is no more catastrophic than the natural death of an individual, why should the birth of a species be any more miraculous than the birth of an individual ? It is quite clear that this thought was vividly present to Darwin when he was writing out his early thoughts in the 1837 Note Book :

Propagation explains why modern animals same type as extinct, which is law almost proved.

1 See the extracts in Life and Letters of Charles Darwin, ii. p. 5.

? The second volume,-especially important in regard to Evolution,reached him in the autumn of 1832, as Prof. Judd has pointed out in his most interesting paper in Darwin and Modern Science. Cambridge, 1909.

* Obituary Notice of C. Darwin, Proc. R. Soc. vol. 44. Reprinted in Huxley's Collected Essays. See also Life and Letters of C. Darwin, ii.

* See the extracts in the Life and Letters, ii. p. 5.

p. 179.

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