Darwin's Origin of species, fourth edition (1866)

An introduction by Gordon Chancellor

This edition was a relatively small printing of 1,500 copies. Darwin began work on it in March 1866 and it appeared in December. Since the appearance of the third edition he had also published Orchids in 1862 and Climbing plants in 1865.

The fourth edition is externally similar to previous editions, but recognisable by some simplification of the cover design, with most copies having 'ORIGIN' and 'SPECIES' in italics on the spine. It looks different internally too, with new centred chapter sub-headings and whiter paper on which the ink has not taken too well in places. It is 52 pages or 16,000 words longer than the third edition, representing the second largest increase in the Origin, the largest being the sixth which gained a whole new chapter. The fourth contains 21 per cent of all the changes made over the editions, with 36 sentences dropped, 435 added and 1,073 altered. Many of the changes were the addition of sizeable new paragraphs.

In the 'Historical Sketch' of this edition, Darwin first attacks the anatomist Richard Owen in print. Having first added acknowledgement that William Wells had published a paper in 1818 which discussed natural selection in the context of humans, Darwin on page xviii expresses great surprise that Owen was claiming in a letter to the London Review in May 1866 that he (rather than Darwin) was the first to publish the theory of natural selection, in the Transactions of the Zoological Society for 1850. Darwin found this surprising because he said Owen in 1850 was only talking about survival, not about the process of evolution, and had been perhaps the most hostile critic of the Origin ever since it had appeared. Darwin had cause to return to this spat in the fifth edition.

The first changes worthy of note here are the addition of several statements in chapter two that many species, especially in plants and insects, come in various different forms. Darwin cites Alfred Russel Wallace on butterflies in this connection and De Candolle on different forms of oak. There are some insertions on the subject of perfection in chapter four and various fascinating facts added on domesticated animals in chapter five, such as the correlation of blue eyes and deafness with white fur in cats. Darwin adds material about striping in horses and even refers to his own horse breeding experiments.
There are many changes to chapter six, concerning for example the early forms of eyes and the different powers of movement in plants. There is a wonderful passage in response to Fritz Müller's work on air breathing crustacea, which had itself been done in response to the Origin:

Hence it might have been expected from mere analogy that the equally important air-breathing apparatus would have been the same in the few species in both families which are thus furnished; and this might have been the more confidently expected by those who believe in the creation of each separate species; for why should this one apparatus, given for the same special purpose to a few species which are so closely similar or rather identical in all other important points, have been made to differ? (p. 227)

Darwin on page 229 refers to the amazing variety of seed dispersal mechanisms in plants which he says are like 'the toys in a shop'. He is amazed by Dr Crüger's finding that one extraordinary orchid to achieve fertilisation forces bees to get soaking wet by blocking their passage with water! The point about these incredibly varied adaptations is that the same end can be achieved in multiple ways from multiple origins. Why, asks Darwin, 'should there be so much variety and so little novelty?', if the adaptations were created rather than constructed piece by piece by natural selection. He ridicules statements that adaptations in nature, such as flowers and fruit, have been created beautiful so as to delight man by stating that flowers are mainly to attract insects and fruits are mainly to attract birds. He refers to the different standards of beauty in the different races of humans (this line of reasoning is discussed at length in Descent of Man) and points out that beautiful molluscs evolved many millions of years before humans:

Were the beautiful volute and cone shells of the Eocene epoch, and the gracefully sculptured ammonites of the Secondary period, created that man might ages afterwards admire them in his cabinet? (p. 239)

In chapter seven Darwin adds material about cuckoo instincts, then in chapter eight he begins to add considerable new material about the origins of hybrid sterility. He cites recent French experiments suggesting that hares and rabbits can interbreed, then develops his earlier view that interspecific sterility cannot be the result of natural selection acting on individual organisms. He implies that it must be operating at a higher level, that of varieties:

It would clearly be advantageous to two varieties or incipient species, if they could be kept from blending, on the same principle that, when man is selecting at the same time two varieties, it is necessary that he should keep them separate. (p. 310)

Darwin then develops a new section on 'reciprocal dimorphism and trimorphism' in plants, a subject he was researching at this time (van Wyhe 2009) including the equivalent of several new pages starting on page 321.
In chapter nine there are fewer changes, but Darwin backtracks fairly dramatically from his life-long commitment to the supremacy of wave action as the main force of erosion of the land. In the face of new research he deletes several passages from previous editions, showing characteristic honesty in the face of overwhelming factual evidence. He also cites a delightful illustration by James Croll using a strip of paper 83 feet long to demonstrate the vastness of geological time.

Darwin also notes the palaeontologist Hugh Falconer's view that although we may think the time over which species change is long, it may be very short compared to the total life span of species. It is interesting that in Darwin's own copy of this edition he has made a note on the inside back cover about this reference. He also introduces some important recent finds of 'intermediate' fossils, such as of the feathered Jurassic dinosaur Archaeopteryx, and the Precambrian Eozoon canadense, described by his friend William Carpenter (although some other palaeontologists did not believe Eozoon was a fossil).

There are few notable changes in chapter ten but in eleven Darwin adds some material about the long-distance dispersal of plants, citing some seeds found in the mud caked on to a partridge's leg. He also adds 'astonishing facts' from his friend J.D. Hooker and the Rev. R.T. Lowe concerning cases where climate change has caused what are now called 'relict' distributions of plants isolated from their original countries of origin. Darwin also adds significant new paragraphs to his discussion of the effects of the Ice Ages on plant distribution. In chapter twelve he makes many small additions concerning dispersal and he cites Baron Aucapitaine's experiment which proved that snails with opercula can survive immersion in sea water for weeks, thus allowing them to be transported on floating flotsam.
In chapter thirteen there are again very many small changes and Darwin mentions his proof – discussed in Orchids - that a species of orchid previously thought to have been three separate genera, actually has male, female and hermaphrodite forms. Probably the most significant additions in this chapter relate to H.W. Bates's description of mimicry in butterfly species on the Amazon, which Darwin calls 'the most remarkable case of analogical resemblance ever recorded' (p. 503). Darwin had been delighted in 1863 with Bates' discovery which was one of the first public declarations of support for Darwin's theory of natural selection. There is also an important series of insertions referring to the zoological work of John Lubbock, Fritz Müller and others on various subjects including alternation of generations, metamorphosis, rudimentary organs, and homology proving community of descent.

Finally, there are many minor but rather few major changes to chapter fourteen, and we close with the following arresting quote where Darwin counters the view that nature is created to be beautiful to man:
That there are exceptions according to our ideas of beauty, no one will doubt who will look at some of the venomous snakes, at some fish, and at certain hideous bats with a distorted resemblance to the human face. (p. 557)

1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: Murray. 4th ed. Text Image PDF F385

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