[320] "Considérations sur quelques principes relatifs à la classification naturelle des animaux," Ann. Sci. nat. (3) i., p. 65, 1844.
[321] Supra, pp. 79-83. Also Précis d'anatomie transcendante, principes d'organogénie, Paris, 1842.
[322] The inversion of the organs shown by Vertebrates as compared with Invertebrates is due to the reversed position of the embryo relatively to the yolk! (pp. 821-6).
[323] It is worth while recording that Serres enunciated a "law of symmetry" according to which the embryo is formed by the union of its two symmetrical halves—a law which recalls the "concrescence theory" of His and some modern embryologists.
[324] "Embryologie comparée du Brochet, de la Perche, et de l'Ecrévisse," Ann. Sci. nat. (4), i., p. 237, 1854; ii., p. 39, 1854. Mém. Savans etrangers, xvii.
[325] Ann. Sci. nat. (4) xvi., p. 113, 1861; xvii., p. 88, 1862; xviii., p. 5, 1862; xix., p. 5, 1863.
[326] xx., p. 5, 1863.
[327] Particularly in his Blennius (1833) and Natter (1839).
[328] In the "preliminary notice" of his Crayfish paper—Isis, pp 1093-1100, 1825.
[329] "On the Anatomy and the Affinities of the Family of the Medusæ," Phil. Trans., 1849; Sci. Memoirs, i., pp. 9-32.