Zool. Pl. cnidæ. [mod.L., a. Gr. κνίδη nettle.] The nettle cell (urticating, or thread cell) of the Cœlenterata (jelly-fish, hydra, etc.), in which their power of stinging resides: usually called nematocyst. Hence [combining form cnido-], Cnidoblast [Gr. βλαστός germ], the cell in which a nematocyst is developed. Cnidocell = cnida. Cnidocil [L. cilium, cf. CIL], the external irritable ciliary process of a cnidoblats. Cnidophore [Gr. -φορος bearing], a process bearing a ‘battery’ of cnidoblasts.
1876. Macalister, Anim. Morphol., 80. In the protoplasmic ectoderm exist scattered or clustered nettle-cells (cnidæ or trichocysts) which are minute oval capsules filled with fluid … lined by a delicate membrane which at the apex is involuted into an axial tube, ending in a long coiled barbed thread.
1884. Sedgwick & Heathcote, trans. Claus’ Elem. Zool., I. 223. Each Cnidoblast … possesses a fine superficial plasmatic process (Cnidocil), which is probably very sensitive to mechanical stimuli, and occasions the bursting of the capsule.
1887. Rolleston & Jackson, Forms Anim. Life, 331. The nematocysts are removed from the cells or cnidoblasts in which they were developed, and where they usually remain until discharged. Ibid. The discharge of the thread is therefore brought about through … direct mechanical or chemical irritation of the cnidocil. Ibid., 757. Some of the hydranths are furnished with a single basal horn-like process—the cnidophore—armed terminally with a battery of cnidoblasts.
