(b. Avignon, France, 13 May 1854; d. Sceaux, France, 7 October 1920)
zoology, anatomy, physiology, embryogeny, general biology.
After passing his baccalauréat ès-sciences and beccalauréat ès-lettres, Delage went to Paris in 1873 to study medicine. Obliged to interrupt his studies, he accepted a post as répétiteur at the lycée of La Rochelle. In 1875 he was able to resume his medical studies. At the same time he prepared for the licence in natural sciences, which he obtained in 1878. In the same year his teacher, Lacaze Duthiers, chose him to direct the zoological station at Roscoff. He defended his doctoral theses in medicine and in science in 1880 and 1881, respectively. He was chargé des fonctions de maître de conférences in zoology at the Sorbonne (1880); chargé de cours at Caen (1881); titular professor of zoology at Caen and director of the zoological station at Luc (1884); chargé de cours at the Sorbonne (1885); titular professor of zoology at the Sorbonne (1886), a post he occupied until his death; and director of the marine laboratory at Roscoff (1902).
Delage’s experimental work was drastically curtailed when he suffered a detached retina, and in 1912 he had to give up teaching. Although he became blind, he continued his work.
A disciple of and assistant to Lacaze Duthiers, Delage at first followed the latter’s zoological traditions. His works on crustacean circulation display remarkable skill; and the superb accompanying illustrations are considered classics. The two chief qualities of Delage’s work were already manifest: experimental ingenuity and technical ability, both guided by a tenacious will. His penetrating critical mind enabled him to establish new truths that were quite different from what was then generally accepted. His discoveries regarding the Sacculina and the embryogeny of the sponges are striking evidence of this ability. The inoculation of the kentrogon larva of the Sacculina and the inversion of the laminae in the metamorphosis of sponges are major discoveries that have withstood the test of time. Also worthy of mention are his researches on the nervous systems of the Peltogaster and of the Convoluta, and on the transformation of a leptocephalus into an eel, which provided the key to the metamorphoses of the Anguillidae; an anatomical study of the Balaenoptera; and a monograph on the ascidians.
In experimental physiology Delage investigated the function of the otocysts in various animals and of the semicircular canals in man. He established a new conception in the physiology of the inner ear: the semicircular canals stabilize equilibrium.
A crisis of conscience led Delage to abandon pure zoology for general biology and biomechanics. He now investigated the causes of the manifestations of life in the cell, in the individual, and in the species, considering this area more productive of important results. The book La structure du protoplasma... (1895) marks the turning point of his scientific career.
The qualities evident in Delage’s earlier works are also present in those on merogony, fertilization, and artificial parthenogenesis. He would not consider a question without completely settling it. After Jacques Loeb’s discovery of artificial fertilization Delage, through theoretical insights, devised a process of chemical fertilization so perfect that for two years he succeeded in raising to the adult stage sea urchins obtained by this process.
Because of the great importance that he accorded to the action of the environment and to the role of acquired characteristics, Delage was a Lamarckian and, therefore, unwilling to accept the ideas of Weismann and Mendel.
Delage founded the Année biologique to publish articles on general biology and was its director for fifteen years. He also planned a great zoological treatise based on his belief that each division of the animal kingdom could be reduced to an ideal type that embodied all the fundamental characteristics of that division.
Among his other activities, Delage constructed and experimented with a bathyrheometer designed to measure the speed of ocean currents. After his blindness had condemned him to meditation, Delage concerned himself with the causes and various states of dreaming.
Delage was not merely an incomparable professor who gave illuminating lectures; he was also a philosopher, a novelist, a short-story writer, a poet, and a polemicist. He belonged to many scientific academies and societies and was elected to the Académie des Sciences in 1901. He worked unceasingly at Roscoff to enlarge the biological station, and there is a monument to him there.
I. Original Works. Among Delage’s papers are “Sur l’origine des éléments figurés du sang chez les Vertébrés”(1880), his M.D. thesis; “Contributions à l’étude de l’appareil circulatoire des Crustacés Edriophthalmes marins,” in Archives de zoologie expérimentale et générale, 9 (1881), 1–176, his thesis for the doctoratés-sciences; “Circulation et respiration chez les Crustacés Schizopodes,” ibid., 2nd ser., 1 (1883), 105–131; “Évolution de la Sacculine,” ibid., 2 (1884), 417–737; “Sur le systéme nerveux et sur quelques autres points de l’organisation du Peltogaster,” ibid., 4 (1886), 17–37; “Études expérimentales sur les illusions statiques et dynamiques de direction pour servir à déterminer les fonctions des canaux semi-circulairesde l’oreille interne,” ibid., 535–695; “Sur une fonction nouvelle des otocystes comme organes d’orientation locomotrice,” ibid., 5 (1887), 1–26; “Études sur les Ascidies des côtes de France; les Cyntiadées,” in Mémoires de l’Académiedes sciences, 2nd ser., 45 (1892–1899), 323 pp., written with Lacaze Duthiers; “Embryogénie des Éponges. Développement post-larvaire des Éponges siliceuses et fibreuses,” in Archives de zoologie expérimentale et générale, 2nd ser., 10 (1893), 345–499; “Étude sur la mérogonie” ibid., 3rd ser., 7 (1899), 383–418; and “La parthénogenése expérimentale,” in Rapport du Congrés zoologique. Graz 1910 (1912), pp. 100–162.
Delage’s books include La structure du protoplasma, les théories sur l’hérédité et les grands problémes de la biologie générale (Paris, 1895); Traité de zoologie concréte, written with E. Hérouard, composed of the following volumes: La cellule et les Protozoaires (Paris, 1896), Les Vermidiens (Paris, 1897), Les Procordés (Paris, 1898), Mesozoaires et Spongiaires (Paris, 1899), Coelentérés (Paris, 1901), and Échinodermes (Paris, 1903); Les théories de l‘évolution, in the Bibliothéque de Philosophic Scientifique (Paris, 1909), written with M. Goldsmith; La parthénogenése naturelle et expérimentale, in Bibliothéque de Philosophie Scientifique (Paris, 1913), written with M. Goldsmith; and Le rêve.Étude psychologique, philosophique et littéraire (Paris,1920).
II Secondary Literature. A notice on the life and work of Delage is M. Goldsmith, in Année biologique, n.s.1 (1920–1921), v–xix. L. Joubin’s speech at the unveiling of the monument to Delage at Roscoff, a biographical notice, and a bibliography constitute Académie des sciences (1924), no. 17. The speeches by both Charles Pérez and L. Joubin at the unveiling of the monument are in Travaux de la Station biologique de Roscoff, 5 (1926), 1–30.