retroflected a. [L. retro, backwards; flectere, to bend] Bending in different directions; bent or turned backwards.
retrogressive development Developmental trend in evolution resulting in simplification of an organism, usually through the complete or partial loss of one or more structures; regressive development.
retrorse a. [L. retrorsus, turned or bent backwards] Turned, bent, or directed backward; backward projecting. see an-trorse, detrorse.
retrovesicular ganglion (NEMATA) The largest ganglion, usu ally posterior to the excretory pore.
retuse a. [L. retusus, blunt] Terminating in a round end or apex with a slight depression.
reunion n. [L. re, back; unire, to make one] Rejoining of broken chromosomes with structural changes.
reversed a. [L. reversare, to turn about] 1. Contrary to the usual. 2. (ARTHRO: Insecta) Deflexed wings; margins of hind wings projecting beyond those of the fore wings. 3. (MOLL) A spiral shell turned in the opposite direction; sinis-tral. see dextral.
reverse mutation Heritable mutation in a gene that returns it to its original function.
reversion n. [L. re, back; vertere, to turn] A genotypic or phe-notypic return to the wild-type of a mutant, may be either partial or complete. revertant a.
reviviscence n. [L. re, back; vivere, to live] The act of reviving; awakening from hibernation, torpor or dessication. re-viviscent a.
revolute a. [L. re, back; volutus, turn around] Curled or rolled backwards, or downwards. see involute.
revolving a. [L. re, back; volutus, turn around] 1. To come around again. 2. (MOLL) Spiral lines on a shell that run parallel with the sutures.
rhabd n. [Gr. rhabdos, rod] (PORIF) A megasclere triaene with an odd, generally straight ray.
rhabdiferous cell (PORIF) A cell that secretes mucopolysac-charide.
rhabdion n. [Gr. rhabdos, rod] (NEMATA) That cuticularized portion of the wall of the stoma. see cheilorhabdions, prorhabdion, mesorhabdions, metarhabdions, telor-habdions.
rhabdites n.pl. [Gr. rhabdos, rod] 1. Rod or blade-like processes projecting from the epidermis. 2. (PLATY: Turbellaria) Straight or slightly curved rods in the epidermis and subepidermis.
rhabditiform a. [Gr. rhabdos, rod; L. forma, shape] Having the shape of a rod.
rhabditoid a. [Gr. rhabdos, rod] (NEMATA: Secernentea) Having characters of free-living bacterial feeding nematodes in the genus Rhabditis.
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