preformation
(priːfɔːˈmeɪʃən)
Also præ-.
[f. pre- A. 2 + formation; cf. preform. So F. préformation (18th c. Bonnet in Littré).]
1. The action or process of forming or shaping beforehand; previous formation.
| 1732 Hist. Litteraria IV. 195 It is easy to think that the Soul is a divine Automaton, still more wonderful, and that by a divine Præformation it produces these beautiful Ideas. 1819 Coleridge Rem. (1836) II. 193 The inauspicious influences on the preformation of Edmund's character. 1838 Sir W. Hamilton Logic xxx. (1866) II. 129 The blind preformations of opinion. 1905 Brit. Med. Jrnl. 25 Feb. 442 On the other hand, the egg of Nereis..and of Beröe..showed a high degree of ‘preformation’, and the early blastomeres of these eggs were not equipotential. |
2. theory of preformation (Biol.): the theory, prevalent in the 18th c., that all the parts of the perfect organism exist previously formed in the germ, and are merely ‘developed’ or unfolded (not produced by accretion) in the process of reproduction. Formerly also called theory of evolution (6 b); opposed to that of epigenesis.
| 1831 Blackw. Mag. XXIX. 68 The two styles of conversation corresponded to the two theories of generation,—one (Johnson's) to the theory of Preformation (or Evolution)—the other (Burke's) to the theory of Epigenesis. 1847 [see epigenesis]. 1879 tr. Haeckel's Evol. Man I. ii. 40 Caspar Friedrich Wolff..with his new Theory of Epigenesis gave the death-blow to the entire Theory of Preformation. 1899 Thomson Sci. Life x. 119 His [Bonnet's] central idea was the ‘preformation’ or asserted pre-existence of the organism and all its parts within the germ. |