ISIDORE GEOFFROY SAINT-HILAIRE (1805-61), a French zoologist, son of the preceding [ETIENNE GEOFFROY SAINT-HILAIRE], Vww at Jardin des Plantes, Paris, December 16, 1805. In his earlier years he showed an aptitude for mathematics, but eventually he devoted himself to the study of natural his-tory and of medicine, and in 1824 he was appointed assist-ant naturalist to his father. On the occasion of his taking the degree of doctor of medicine, September 8, 1829, he read a thesis entitled Propositions sur la monstruosité, considérée chez l'homme et les animaux; and in 1832-37 was published his great teratological work, Histoire générale et particulière des anomalies de l'organisation chez l'homme et les animaux, 3 vols. 8vo, with 20 plates. In 1829 he delivered for his father the second part of a course of lectures on ornithology, and during the three following years he taught zoology at the Athénée, and teratology at the École pratique. He was elected a member of the academy of sciences at Paris on April 15, 1833, was in 1837 appointed to act as deputy for his father at the faculty of sciences in Paris, and in the following year was sent to Bordeaux to organize a similar faculty there. He became successively inspector of the academy of Paris (1840), professor of the museum on the retirement of his father, inspector general of the university (1844), a mem-ber of the royal council for public instruction (1845), and, on the death of Blainville, professor of zoology at the faculty of sciences (1850). In 1854 he founded the Acclimatization Society of Paris, of which he was president. He died at Paris, November 10, 1861.
Besides the above-mentioned works, he wrote Essais de Zoologie générale, 1841; Vie. . . . d'Etienne Geoffroy Saint-Hilaire, 1847; Acclimatation et Domestication des Animaux utiles, 1849, 4th éd., 1861 ; Lettres sur les substances alimentaires et particulièrement sur la mande de cheval, 1856 ; and Histoire naturelle générale des règnes organiques, 3 vols., 1854-62, which was not completed, chap. xx. of tome iii. being unfinished. He was the author also of various papers on zoology, comparative anatomy, and palaeontology, pub-lished for the most part in the Annales du Muséum, the Mémoires des Savants étrangers, the Comptes rendus, and the Diet, des Sciences naturelles.