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[[文件:Charles-Darwin-and-William-Darwin,-1842.png|缩略图|右|1842年，达尔文与长子威廉·伊拉斯谟·达尔文William Erasmus Darwin。]]

[[文件:Charles-Darwin-and-William-Darwin,-1842.png|缩略图|右|1842年，达尔文与长子威廉·伊拉斯谟·达尔文William Erasmus Darwin。]]

Darwin now had the framework of his theory of natural selection "by which to work",<ref name="autobio 120" /> as his "prime hobby".<ref name=Letter419>{{cite web|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-419.html|title=Darwin Correspondence Project&nbsp;– Letter 419&nbsp;– Darwin, C. R. to Fox, W. D., (15 June 1838)|accessdate=8 February 2008|url-status=live|archiveurl=https://web.archive.org/web/20070904124133/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-419.html|archivedate=4 September 2007}}</ref> His research included extensive experimental selective breeding of plants and animals, finding evidence that species were not fixed and investigating many detailed ideas to refine and substantiate his theory.<ref name=JvW /> For fifteen years this work was in the background to his main occupation of writing on geology and publishing expert reports on the ''Beagle'' collections, and in particular, the barnacles.<ref name=vw186>{{Harvnb|van Wyhe|2007|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=A544&pageseq=10 186–192]}}</ref>

Darwin now had the framework of his theory of natural selection "by which to work",<ref name="autobio 120" /> as his "prime hobby".<ref name=Letter419>{{cite web|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-419.html|title=Darwin Correspondence Project&nbsp;– Letter 419&nbsp;– Darwin, C. R. to Fox, W. D., (15 June 1838)|accessdate=8 February 2008|url-status=live|archiveurl=https://web.archive.org/web/20070904124133/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-419.html|archivedate=4 September 2007}}</ref> His research included extensive experimental selective breeding of plants and animals, finding evidence that species were not fixed and investigating many detailed ideas to refine and substantiate his theory.<ref name=JvW /> For fifteen years this work was in the background to his main occupation of writing on geology and publishing expert reports on the ''Beagle'' collections, and in particular, the barnacles.<ref name=vw186>{{Harvnb|van Wyhe|2007|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=A544&pageseq=10 186–192]}}</ref>

Darwin's "sandwalk" at [[Down House was his usual "Thinking Path".]]

Darwin now had the framework of his theory of natural selection "by which to work",[97] as his "prime hobby".[103] His research included extensive experimental selective breeding of plants and animals, finding evidence that species were not fixed and investigating many detailed ideas to refine and substantiate his theory.[13] For fifteen years this work was in the background to his main occupation of writing on geology and publishing expert reports on the Beagle collections, and in particular, the barnacles.

When FitzRoy's ''Narrative'' was published in May 1839, Darwin's ''[[The Voyage of the Beagle|Journal and Remarks]]'' was such a success as the third volume that later that year it was published on its own.<ref>{{Harvnb|Darwin|1887|loc=[http://www.gutenberg.org/catalog/world/readfile?fk_files=39003&pageno=32 p. 32.]}}</ref> Early in 1842, Darwin wrote about his ideas to [[Charles Lyell]], who noted that his ally "denies seeing a beginning to each crop of species".<ref>{{Harvnb|Desmond|Moore|1991|p=292}}</ref>

When FitzRoy's ''Narrative'' was published in May 1839, Darwin's ''[[The Voyage of the Beagle|Journal and Remarks]]'' was such a success as the third volume that later that year it was published on its own.<ref>{{Harvnb|Darwin|1887|loc=[http://www.gutenberg.org/catalog/world/readfile?fk_files=39003&pageno=32 p. 32.]}}</ref> Early in 1842, Darwin wrote about his ideas to [[Charles Lyell]], who noted that his ally "denies seeing a beginning to each crop of species".<ref>{{Harvnb|Desmond|Moore|1991|p=292}}</ref>

By July, Darwin had expanded his "sketch" into a 230-page "Essay", to be expanded with his research results if he died prematurely. In November, the anonymously published sensational best-seller Vestiges of the Natural History of Creation brought wide interest in transmutation. Darwin scorned its amateurish geology and zoology, but carefully reviewed his own arguments. Controversy erupted, and it continued to sell well despite contemptuous dismissal by scientists.

When FitzRoy's Narrative was published in May 1839, Darwin's Journal and Remarks was such a success as the third volume that later that year it was published on its own.[105] Early in 1842, Darwin wrote about his ideas to Charles Lyell, who noted that his ally "denies seeing a beginning to each crop of species".

Darwin's book ''[[The Structure and Distribution of Coral Reefs]]'' on his theory of [[atoll]] formation was published in May 1842 after more than three years of work, and he then wrote his first "pencil sketch" of his theory of natural selection.<ref>{{Harvnb|Desmond|Moore|1991|pp=292–293}}<br />{{Harvnb|Darwin|1842|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F1556&pageseq=18 xvi–xvii]}}</ref> To escape the pressures of London, the family moved to rural [[Down House]] in September.<ref>{{Harvnb|Darwin|1958|p=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F1497&pageseq=118 114]}}</ref> On 11 January 1844, Darwin mentioned his theorising to the botanist [[Joseph Dalton Hooker]], writing with melodramatic humour "it is like confessing a murder".<ref>{{harvnb|van Wyhe|2007|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=A544&pageseq=7 183–184]}}</ref><ref>{{cite web|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-729.html#back-mark-729.f6|title=Darwin Correspondence Project&nbsp;– Letter 729&nbsp;– Darwin, C. R. to Hooker, J. D., (11 January 1844)|accessdate=8 February 2008|url-status=live|archiveurl=https://web.archive.org/web/20080307235150/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-729.html#back-mark-729.f6|archivedate=7 March 2008}}</ref> Hooker replied "There may in my opinion have been a series of productions on different spots, & also a gradual change of species. I shall be delighted to hear how you think that this change may have taken place, as no presently conceived opinions satisfy me on the subject."<ref>{{cite web|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-734.html|title=Darwin Correspondence Project&nbsp;– Letter 734&nbsp;– Hooker, J. D. to Darwin, C. R., 29 January 1844|accessdate=8 February 2008|url-status=live|archiveurl=https://web.archive.org/web/20090226141303/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-734.html|archivedate=26 February 2009}}</ref>

Darwin's book ''[[The Structure and Distribution of Coral Reefs]]'' on his theory of [[atoll]] formation was published in May 1842 after more than three years of work, and he then wrote his first "pencil sketch" of his theory of natural selection.<ref>{{Harvnb|Desmond|Moore|1991|pp=292–293}}<br />{{Harvnb|Darwin|1842|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F1556&pageseq=18 xvi–xvii]}}</ref> To escape the pressures of London, the family moved to rural [[Down House]] in September.<ref>{{Harvnb|Darwin|1958|p=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F1497&pageseq=118 114]}}</ref> On 11 January 1844, Darwin mentioned his theorising to the botanist [[Joseph Dalton Hooker]], writing with melodramatic humour "it is like confessing a murder".<ref>{{harvnb|van Wyhe|2007|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=A544&pageseq=7 183–184]}}</ref><ref>{{cite web|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-729.html#back-mark-729.f6|title=Darwin Correspondence Project&nbsp;– Letter 729&nbsp;– Darwin, C. R. to Hooker, J. D., (11 January 1844)|accessdate=8 February 2008|url-status=live|archiveurl=https://web.archive.org/web/20080307235150/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-729.html#back-mark-729.f6|archivedate=7 March 2008}}</ref> Hooker replied "There may in my opinion have been a series of productions on different spots, & also a gradual change of species. I shall be delighted to hear how you think that this change may have taken place, as no presently conceived opinions satisfy me on the subject."<ref>{{cite web|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-734.html|title=Darwin Correspondence Project&nbsp;– Letter 734&nbsp;– Hooker, J. D. to Darwin, C. R., 29 January 1844|accessdate=8 February 2008|url-status=live|archiveurl=https://web.archive.org/web/20090226141303/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-734.html|archivedate=26 February 2009}}</ref>

Darwin completed his third geological book in 1846. He now renewed a fascination and expertise in marine invertebrates, dating back to his student days with Grant, by dissecting and classifying the barnacles he had collected on the voyage, enjoying observing beautiful structures and thinking about comparisons with allied structures. In 1847, Hooker read the "Essay" and sent notes that provided Darwin with the calm critical feedback that he needed, but would not commit himself and questioned Darwin's opposition to continuing acts of creation.

Darwin's book The Structure and Distribution of Coral Reefs on his theory of atoll formation was published in May 1842 after more than three years of work, and he then wrote his first "pencil sketch" of his theory of natural selection.[107] To escape the pressures of London, the family moved to rural Down House in September.[108] On 11 January 1844, Darwin mentioned his theorising to the botanist Joseph Dalton Hooker, writing with melodramatic humour "it is like confessing a murder".[109][110] Hooker replied "There may in my opinion have been a series of productions on different spots, & also a gradual change of species. I shall be delighted to hear how you think that this change may have taken place, as no presently conceived opinions satisfy me on the subject."

 

 

 

 

[[File:Darwins Thinking Path.JPG|thumb|right|alt=Path covered in sandy gravel winding through open woodland, with plants and shrubs growing on each side of the path.|Darwin's "sandwalk" at [[Down House]] was his usual "Thinking Path".<ref>{{harvnb|Darwin|1887|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F1452.1&pageseq=132 114–116]}}</ref>]]

 

In an attempt to improve his chronic ill health, Darwin went in 1849 to Dr. James Gully's Malvern spa and was surprised to find some benefit from hydrotherapy. Then, in 1851, his treasured daughter Annie fell ill, reawakening his fears that his illness might be hereditary, and after a long series of crises she died.

 

 

 

 

By July, Darwin had expanded his "sketch" into a 230-page "Essay", to be expanded with his research results if he died prematurely.<ref>{{Harvnb|van Wyhe|2007|p= 188}}</ref> In November, the anonymously published sensational best-seller ''[[Vestiges of the Natural History of Creation]]'' brought wide interest in transmutation. Darwin scorned its amateurish geology and zoology, but carefully reviewed his own arguments. Controversy erupted, and it continued to sell well despite contemptuous dismissal by scientists.<ref>{{harvnb|Browne|1995|pp=461–465}}</ref><ref>{{cite web|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-814.html#back-mark-814.f5|title=Darwin Correspondence Project&nbsp;– Letter 814&nbsp;– Darwin, C. R. to Hooker, J. D., (7 Jan 1845)|accessdate=24 November 2008|url-status=live|archiveurl=https://web.archive.org/web/20081205084645/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-814.html#back-mark-814.f5|archivedate=5 December 2008}}</ref>

 

In eight years of work on barnacles (Cirripedia), Darwin's theory helped him to find "homologies" showing that slightly changed body parts served different functions to meet new conditions, and in some genera he found minute males parasitic on hermaphrodites, showing an intermediate stage in evolution of distinct sexes. In 1853, it earned him the Royal Society's Royal Medal, and it made his reputation as a biologist. In 1854 he became a Fellow of the Linnean Society of London, gaining postal access to its library. He began a major reassessment of his theory of species, and in November realised that divergence in the character of descendants could be explained by them becoming adapted to "diversified places in the economy of nature".

 

 

 

 

Darwin completed his third geological book in 1846. He now renewed a fascination and expertise in [[marine invertebrates]], dating back to his student days with [[Robert Edmond Grant|Grant]], by dissecting and classifying the [[barnacle]]s he had collected on the voyage, enjoying observing beautiful structures and thinking about comparisons with allied structures.<ref>{{Harvnb|van Wyhe|2007|pp=190–191}}</ref> In 1847, Hooker read the "Essay" and sent notes that provided Darwin with the calm critical feedback that he needed, but would not commit himself and questioned Darwin's opposition to continuing acts of [[creation myth|creation]].<ref>{{Harvnb|Desmond|Moore|1991|pp= 320–323, 339–348}}</ref>

 

 

 

In an attempt to improve his chronic ill health, Darwin went in 1849 to Dr. [[James Manby Gully|James Gully]]'s [[Great Malvern|Malvern]] spa and was surprised to find some benefit from [[hydrotherapy]].<ref>{{cite web|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-1236.html|title=Darwin Correspondence Project&nbsp;– Letter 1236&nbsp;– Darwin, C. R. to Hooker, J. D., 28 Mar 1849|accessdate=24 November 2008|url-status=live|archiveurl=https://web.archive.org/web/20081207005457/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-1236.html|archivedate=7 December 2008}}</ref> Then, in 1851, his treasured daughter [[Anne Darwin|Annie]] fell ill, reawakening his fears that his illness might be hereditary, and after a long series of crises she died.<ref>{{harvnb|Browne|1995|pp=498–501}}</ref>

 

Charles Darwin, aged 46 in 1855, by then working towards publication of his theory of [[natural selection. He wrote to Hooker about this portrait, "if I really have as bad an expression, as my photograph gives me, how I can have one single friend is surprising."]]

 

 

 

 

By the start of 1856, Darwin was investigating whether eggs and seeds could survive travel across seawater to spread species across oceans. Hooker increasingly doubted the traditional view that species were fixed, but their young friend Thomas Henry Huxley was still firmly against the transmutation of species. Lyell was intrigued by Darwin's speculations without realising their extent. When he read a paper by Alfred Russel Wallace, "On the Law which has Regulated the Introduction of New Species", he saw similarities with Darwin's thoughts and urged him to publish to establish precedence. Though Darwin saw no threat, on 14 May 1856 he began writing a short paper. Finding answers to difficult questions held him up repeatedly, and he expanded his plans to a "big book on species" titled Natural Selection, which was to include his "note on Man". He continued his researches, obtaining information and specimens from naturalists worldwide including Wallace who was working in Borneo. In mid-1857 he added a section heading; "Theory applied to Races of Man", but did not add text on this topic. On 5 September 1857, Darwin sent the American botanist Asa Gray a detailed outline of his ideas, including an abstract of Natural Selection, which omitted human origins and sexual selection. In December, Darwin received a letter from Wallace asking if the book would examine human origins. He responded that he would avoid that subject, "so surrounded with prejudices", while encouraging Wallace's theorising and adding that "I go much further than you."

 

 

In eight years of work on [[barnacle]]s (Cirripedia), Darwin's theory helped him to find "[[homology (biology)|homologies]]" showing that slightly changed body parts served different functions to meet new conditions, and in some [[genus|genera]] he found minute males [[parasitism|parasitic]] on [[hermaphrodite]]s, showing an [[Androdioecy|intermediate stage]] in evolution of [[Gonochorism|distinct sexes]].<ref name=barlowbio117>{{Harvnb|Darwin|1958|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F1497&pageseq=121 117–118]}}</ref> In 1853, it earned him the [[Royal Society]]'s Royal Medal, and it made his reputation as a [[biology|biologist]].<ref>{{Harvnb|Desmond|Moore|1991|pp= 383–387}}</ref> In 1854 he became a Fellow of the [[Linnean Society of London]], gaining postal access to its library.<ref>{{harvnb|Freeman|2007|pp=107, 109}}</ref> He began a major reassessment of his theory of species, and in November realised that divergence in the character of descendants could be explained by them becoming adapted to "diversified places in the economy of nature".<ref>{{Harvnb|Desmond|Moore|1991|pp= 419–420}}</ref>

 

===Publication of the theory of natural selection===

===Publication of the theory of natural selection===