retractor spiculi (NEMATA) Paired spicular muscles, each containing a nucleus in the sarcoplasm, arising from the spi-
cular head and extending to the hypodermis in the region of the lateral chords.
retroarcuate a. [L. retro, backwards; arcuare, to bow] Curved backwards.
retrobursal a. [L. retro, backwards; bursa, purse] (PLATY: Tur-bellaria) In Tricladida, having the bursal stalk short, so that the bursa lies behind the penis; retrobursalia. see probur-sal.
retrocerebral endocrine system (ARTHRO: Insecta) System comprised of corpora allata, corpora cardiaca and ventral gland.
retrocerebral organ (ROTIF) A small glandular organ, attached to the epidermis above and behind the brain, comprised of the retrocerebral sac and the subcerebral glands; function unknown.
retrocerebral pore (CHAETO) A pore on the dorsal surface behind the brain where the rectocerebral organs open.
retrocerebral sac 1. (CHAETO) A pair of sacs imbedded in the posterior part of the cerebral ganglion, separated by a membrane but connected by a nerve proximally, and opening by means of the retrocerebral pore. 2. (ROTIF) A forked duct opening on the apical field, often on a single or paired papilla; part of the retrocerebral organ.
retrocession n. [L. retro, back; cedere, to go] The act of ret-roceding; to move backward.
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