In 1959, 100 years after the publication of the first edition of Darwin's The Origin of Species, the University of Pennsylvania Press published a 'Variorum Text', edited by Morse Peckham, containing all the variants in the six editions published during Darwin's lifetime. Anyone who reads historical studies of Darwin's work will have seen references to the Variorum edition, but the book itself has been out of print and virtually unobtainable for many years. I have occasionally seen it in bookdealers' lists at a price of hundreds of pounds or dollars, but even my enthusiasm for Darwin doesn't run quite that far.

It is therefore a pleasure to report that it has recently been republished in paperback:

Charles Darwin: The Origin of Species: A Variorum Text, edited by Morse Peckham, University of Pennsylvania Press, Philadelphia, 816 pages.

The price is about $30 in the US or £20 in the UK.

I can recommend the book to anyone who wants to make a serious study of the Origin. Let me be clear: it is not a suitable edition for anyone who just wants a reading copy. For this purpose, the text of the first or the sixth editions, both of which are easily available, would be more convenient. The layout of Peckham's Variorum edition is unusual. Each sentence of the first edition text is printed in full, followed by any amendments or additions in each of editions 2 - 6 in turn. Often this means that a whole page or more is devoted to one sentence of the original text. This makes it difficult (though not impossible) to follow a continuous text of any of the editions. I have seen the Variorum edition criticised for this reason, but this is missing the point. As Peckham himself says in his Introduction (page 27) 'this arrangement makes the text difficult to read, but I cannot imagine anyone reading such an edition in order to obtain a general knowledge of the book'. Its purpose is to enable historians and others interested in the development of Darwin's thought, and his reactions to criticisms and new evidence, to trace how this was shown in his revisions of the Origin. For this purpose it seems to me well-designed, and I don't know of any substitute for it. It is true that all six editions of the Origin are now available online from the Darwin Online Project, but even if you can find some way of getting all six texts on screen at the same time, it would be extremely laborious to compare them. One of the most striking lessons of the Variorum text is to show just how much revising Darwin did. As Peckham points out, around three quarters of all the sentences in the first edition were amended, often several times, and as a result of numerous additions the sixth edition is nearly a third as long again as the first.

And yet the substance of Darwin's views is remarkably little changed. The common view that he watered down his emphasis on natural selection in favour of 'Lamarckism' does not stand up to examination: changes in this direction are few, and do not greatly affect the balance of the book.

So congratulations to the publishers for making this available again.