In ‘canvassing Cuvier’ and ‘harnessing Humboldt’, Sarah's remarkable book-length pub-lications from 1825 have clearly demonstrated in chapter studies thus far how she crea-tively developed their different (world-leading) expertise and parallel scientific priorities – in the Muséum; in the intercontinental field respectively – for optimal contribution to leading natural history endeavour outside its many bars to women on both sides of the Channel. The leanest period for her scientific contributions after the last numbers of the Fresh-Water Fishes (1838–1839) and publication of Elements of Natural History (1844) then starkly stands out. It coincided with the final illness and death of Sarah's mother as Donald deB. Beaver has clarified, but his DNB entry cannot then explain how she ‘entered on her most prolific period of writing […] (both fiction and non-fiction), for both children and adults’. Sarah's natural history expedition ‘in forty-four British Fishes’ (Chapter 2) had no (commissioned) field project at home to replace it. How was her new work in natural history after 1839 inspired and fostered by experts and leading peer communities as the constant benchmark for her contributions since 1825?

Chapters in this final part address both the ‘gap’ that is 1839–1844 and its pivotal impor-tance for the ‘most prolific’ last decade of Sarah's work(s) in natural history. The enduring significance of both Cuvier and Humboldt as her ‘French’ mentors and models lay also in their common cause for world natural history-making, namely to enhance its under-standing in two interconnecting ways. First was their unwavering commitment to science pedagogy and wider public dissemination of new scientific knowledge, in order to inspire newcomers besides informing experts. Among Cuvier's many functions as the Chair in Comparative Anatomy at the Paris Muséum were his public lectures and demonstrations, with women in these audiences. His famed reconstructions of extinct fossil creatures from a single tooth or bone that demonstrated his new classifications of vertebrate life forms were one with his curation of the Galleries of Comparative Anatomy and Palaeontology for expert and general public understanding. In the second part of her Memoirs, Sarah had accounted for his ‘pedagogical’ publications (also listed in its bibliography of Cuvier's many works) as summed up in the ‘Tableau Elémentaire, and the two editions of the Règne Animal, as different stages of the same work, and, with the Fossil Remains, and Natural History of Fishes, as the results of his discoveries in comparative anatomy.