In spite of its age, Agassiz’s Essay is still worth reading today. It first appeared in 1857 as a chapter in the first volume of Contributions to the Natural History of the United States. Its publication in book form, two years later, could not have been more unfortunately timed, coinciding with the publication of Darwin’s Origin.

The Essay has been reprinted on several occasions, notably in 1962 by The Belknap Press of Harvard University Press, with an introduction by Edward Lurie, Agassiz’s first biographer (1960, Louis Agassiz: A Life in Science, University of Chicago Press, reprinted in 1988; this biography is still worth reading). The 1962 reprint was republished in 2004 by Dover Press. Both the 1859 and 1962 editions are available via the Biodiversity Heritage Library (BHL), as is the earlier version published in Contributions to the Natural History of the United States (volume 1, 1857).

Of further interest is a French language edition published near the end of Agassiz’s life (Agassiz 1869. De l'espèce et de la classification en zoologie, translated by Felix Vogeli, Bailière, Paris; also available at BHL). This edition includes an additional chapter that never appeared in the English editions where Agassiz discusses his objections to Darwin’s views on evolution and where he re-casts some of Haeckel’s phylogenetic diagrams (for further discussion see Morris, PJ., 1997. Louis Agassiz’s additions to the French translation of his Essay on Classification. Journal of the History of Biology 30: 121–134, which includes some passages translated into English; Williams & Ebach (2007), cited below, comment on the relevance of some of these passages).

Two good books dealing with aspects of Agassiz’s intellectual development, both written by Winsor, are: 1976. Starfish, Jellyfish, and the Order of Life: Issues in Nineteenth Century Science. Yale University Press, New Haven CT; 1991. Reading the Shape of Nature: Comparative Zoology at the Agassiz Museum. University of Chicago Press, Chicago; also Irmscher, C. 2013. Louis Agassiz: Creator of American Science. Houghton Mifflin Harcourt, Boston, New York.

Candolle’s Théorie … is still one of the best introductions to the distinction between artificial and natural classifications, being ‘the first work in which the soul of the natural and artificial method had been laid bare’ (Croizat 1945, p. 64). An English translation was published in 1821 (Candolle and Sprengel 1821), derived from an earlier German translation (Candolle and Sprengel 1820) – Candolle was unhappy with both. William Whewell (Whewell, W. 1840. The Philosophy of the Inductive Sciences. J.W. Parker, London; Whewell, W. 1847. The Philosophy of the Inductive Sciences, Founded upon Their History. J.W. Parker, London) summarised some of Candolle’s ideas and a brief account is given in Williams et al. (2010) and in our Chapter 7. No accurate (or acceptable) English translation exists of Théorie élémentaire de la botanique; one is much needed.

Lecointre & Le Guyader produced a comprehensive account of the diversity and classification of all organic life, including short summaries of each taxon recognised. The version cited here is derived and updated from the French edition of Classification phylogénétique du vivant, first published in 2001 (the 2nd edition was published in 2002, the 3rd in 2006). The English language translation is of the 3rd French edition.

This is an excellent account of developments in evolutionary ideas in France written by a scientist who worked at the Muséum national d'Histoire naturelle. Although a little dated, it is still a useful book to consult providing insight into the complexities of the comparative biology of a previous time. It is available in an English translation: The Philosophy of Zoology Before Darwin: A translated and annotated version of the original French text by Edmond Perrier (2009, translated by Alex McBirney, with annotations by Stanton Cook and Gregory Retallack, Springer).

This is an excellent account of developments in the understanding and construction of artificial and natural methods in classification. Scharf writes: ‘British botanists, however, continued to use Linnaeus’s sexual system almost exclusively for another two decades. Their reluctance to use other methods or systems of classification can be attributed to a culture suspicious of innovation, anti-French sentiment and the association of all things Linnaean with English national pride, fostered in particular by the President of the Linnean Society of London, Sir James Edward Smith. The British aversion to using multiple plant identification technologies in one text also helps explain why it took so long for English botanists to adopt the natural method, even after several Englishmen had tried to introduce it to their country’.

We include this as it directs attention to the ways in which some students learn about animals and plants, a factor that is of significance when developing useful artificial classifications specifically for taxon identification.

This is a comprehensive account of developments in biological systematics up to 1859 with reference to, and a comprehensive account of, the Natural System. It is still a remarkably useful and accessible account, primarily focusing on developments in botanical classification.