[914] The male salmon is known to breed at a very early age. The Triton and Siredon, whilst retaining their larval branchiæ, according to Filippi and Duméril ('Annals and Mag. of Nat. Hist.,' 3rd series, 1866, p. 157), are capable of reproduction. Ernst Häckel has recently ('Monatsbericht Akad. Wiss. Berlin,' Feb. 2nd, 1865) observed the surprising case of a medusa, with its reproductive organs active, which produces by budding a widely different form of medusa; and this latter also has the power of sexual reproduction. Krohn has shown ('Annals and Mag. of Nat. Hist.,' 3rd series, vol. xix., 1862, p. 6) that certain other medusæ, whilst sexually mature, propagate by gemmæ.
[915] See his excellent discussion on this subject in 'Nouvelles Archives du Muséum,' tom. i. p. 151.
[916] Various physiologists have insisted on this distinction between growth and development. Prof. Marshall ('Phil. Transact.,' 1864, p. 544) gives a good instance in microcephalous idiots, in which the brain continues to grow after having been arrested in its development.
[917] 'Compte Rendu,' Nov. 14, 1864, p. 800.
[918] As previously remarked by Quatrefages, in his 'Metamorphoses de l'Homme,' &c., 1862, p. 129.
[919] Günther's 'Zoological Record,' 1864, p. 279.
[920] Sedgwick, in 'Medico-Chirurg. Review,' April 1863, p. 454.
[921] Isid. Geoffroy St. Hilaire, 'Hist. des Anomalies,' tom. i., 1832, pp. 435, 657; and tom. ii. p. 560.
[922] Virchow, 'Cellular Pathology,' 1860, p. 66.
[923] Moquin-Tandon, 'Tératologie Veg.,' 1841, pp. 218, 220, 353. For the case of the pea, see 'Gardener's Chron.,' 1866, p. 897.