PART III

I.—­Wallace’s Works on Biology and Geographical Distribution

    “I have long recognised how much clearer and deeper your insight
    into matters is than mine.”

    “I sometimes marvel how truth progresses, so difficult is it for
    one man to convince another, unless his mind is vacant.”

    “I grieve to differ from you, and it actually terrifies me, and
    makes me constantly distrust myself.  I fear we shall never quite
    understand each other.”

    —­Darwin to Wallace.

During the period covered by the reception, exposition, and gradual acceptance of the theory of Natural Selection, both Wallace and Darwin were much occupied with closely allied scientific work.

The publication in 1859 of the “Origin of Species"[1] marked a distinct period in the course of Darwin’s scientific labours; his previous publications had, in a measure, prepared the way for this, and those which immediately followed were branches growing out from the main line of thought and argument contained in the “Origin,” an overflow of the “mass of facts” patiently gathered during the preceding years.  With Wallace, the end of the first period of his literary work was completed by the publication of his two large volumes on “The Geographical Distribution of Animals,” towards which all his previous thought and writings had tended, and from which, again, came other valuable works leading up to the publication of “Darwinism” (1889).

It will be remembered that Darwin and Wallace, on their respective returns to England, after many years spent in journeyings by land and sea and in laborious research, found the first few months fully occupied in going over their large and varied collections, sorting and arranging with scrupulous care the rare specimens they had taken, and in discovering the right men to name and classify them into correct groups.

At this point it will be useful to arrange Darwin’s writings under three heads, namely:  (1) His zoological and geological books, including “The Voyage of the Beagle” (published in 1839), “Coral Reefs” (1842), and “Geological Observations on South America” (1846).  In this year he also began his work on Barnacles, which was published in 1854; and in addition to the steady work on the “Origin of Species” from 1837 onwards, his observations on “Earthworms,” not published until 1881, formed a distinct phase of his study during the whole of these years (1839-59). (2) As a natural sequence we have “Variations of Animals and Plants under Domestication” (1868), “The Descent of Man” (1871), and “The Expression of the Emotions” (1872). (3) What may be termed his botanical works, largely influenced by his evolutionary ideas, which include “The Fertilisation of Orchids” (1862), “Movements and Habits of Climbing Plants” (1875), “Insectivorous Plants” (1876), “The Different Forms of Flowers and Plants of the same Species” (1877), and “The Power of Movement in Plants” (1880).