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Online Dictionary of Invertebrate Zoology: Complete Work - Best Text

Online Dictionary of Invertebrate Zoology: Complete Work - Best Text

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746Maggenti and Gardnerprotoscolex n. [Gr. protos, first; skolex, worm] (PLATY:Cestoda) In Taeniidae, a juvenile scolex budded within ahydatid or coenurus metacestode.protosoma, protosome n. [Gr. protos, first; soma, body] 1.(ARTHRO) The prosoma. 2. (POGON) The anterior tentacularregion bearing 1-200 tentacles and including the principalnerve ganglion. see prosome.protospecies n. [Gr. protos, first; L. species, kind] The preexistingtype from which other species evolved.protostasy n. [Gr. protos, first; stasis, standing] (ARTHRO:Chelicerata) In Acari, an orthostasic stage in a life cycle involvingsix stases. see orthostasy.protosternum n. [Gr. protos, first; sternon, chest] (ARTHRO:Chelicerata) In Acari, the sternite <strong>of</strong> the cheliceral segment<strong>of</strong> the prosoma.protostome, protostom n. [Gr. protos, first; stoma, mouth]1. Metazoans with determinate spiral clevage and wherethe mesoderm can be traced to a single cell in the blastula,the mouth originates from the blastopore; includes mollusks,annelids, arthropods, nematodes and certain lesserphyla. see deuterostome. 2. (NEMATA) In rhabditid-likenematodes, the cylindrical midportion <strong>of</strong> the stoma, delimitedanteriorly by the cheilostome and posteriorly by thetelostome; the protostom may be further subdivided into:prostome, mesostome and metastome.Protostomia n. [Gr. protos, first; stoma, mouth] Formerly themain division between bilateral animals, including the mollusks,annelids, and arthropods.protostracum n. [Gr. protos, first; ostrakion, a shell] (MOLL:Bivalvia) 1. In larval forms, the first formed part <strong>of</strong> a prodissoconch.2. In oysters, the shell <strong>of</strong> the D-shaped larvalstage; straight-hinge veliger.protostyle n. [Gr. protos, first; stylos, piller] (MOLL) The stiffmucous rod <strong>of</strong> early mollusks that transports the foodstring along the esophagus into the stomach; the forerunner<strong>of</strong> the crystalline style.prototaxy n. [Gr. protos, first; taxis, arrangement] The arrangement<strong>of</strong> organs in certain areas that are all consid-

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