evocator
(ˈɛvəkeɪtə(r))
[a. L. ēvocātor, agent-n. f. ēvocāre: see evocate.]
a. One who evocates or evokes; esp. one who evokes or calls up a spirit.
| 1794 T. Taylor Pausanias I. 305 [He] went to Phigalea, to the Arcadian evocators of souls. 1817 Byron Manfred ii. ii. 188 He..roused The Arcadian Evocators to compel The indignant shadow to depose her wrath. 1835 Blackw. Mag. XXXVIII. 647 Imagination..like an olden Evocator rears The gorgeous phantoms of forgotten years. |
b. Biochem. and Embryol. A chemical substance in part of an embryo that stimulates the development of another part.
| 1934 J. Needham et al. in Proc. R. Soc. B. CXIV. 409 We suggest that the first type of determination be spoken of as Evocation, since it consists in the evoking of an embryonic axis from the competent ectoderm... The organiser, or the evocator, as it might now be called, is soluble in ether and petroleum ether. 1936 Nature 15 Feb. 251/2 This stimulus, which the author [sc. C. H. Waddington] calls the evocator, is a chemical substance and is not specific for a particular kind of animal. But the tissue acted upon must be in a ‘competent state’ for the evocator to work. 1958 B. M. Patten Found. Embryol. vi. 134 The chemical substance it [sc. the tissue] gives off is known as the organizing substance or evocator. |