sb. pl. Zool. A singular form is ACRITAN. [mod.L., a. Gr. ἄκριτα, pl. neut. of ἄκριτος undistinguishable, sc. animalia.] A name given by MacLeay to a division of the animal kingdom, comprehending the Infusoria, the Polypes, and some of the Intestina; so called from the want of a distinct nervous system. Adopted in 1835 by Owen for a series of the Radiated animals.
1835. Kirby, Habits & Inst. Anim., I. iv. 149. [Infusories also called] Acrita or indiscernibles.
1835. Owen, in Todd, Cycl., s.v., The Acrita have been termed Protozoa, as being on the first step of animal organization.
1837. Whewell, Induct. Sc., III. XVII. vii. § 2. 450. Some naturalists have doubted whether these zoophytes are not referrible to two types (acrita or polypes, and the true radiata), rather than to one.
1879. Chambers, Encycl., s.v. Zoology, The lowest animals, in which no trace of a nervous system has been discovered, have been formed into a separate division of the animal kingdom, under the names Acrita and Protozoa.
