protostoma

plural protostomata

1. obsoleteembryologySynonym of blastopore.

   The opening of this, the protostoma, becomes elongated, taking on an elliptical shape, and then it narrows in the middle, its outline becoming that of a dumb-bell.

   1921, John Graham Kerr, Zoology for Medical Students, page 150

   1 more example

   It is frequently stated by critics of the protostoma hypothesis that it involves a reversal of dorsal and ventral sides during the evolution of Vertebrates from their invertebrate ancestors but it will be gathered from what has been said that this criticism rests on a misunderstanding.

   1919, Ernest William MacBride, Text-book of Embryology

   Synonyms: blastopore

2. biologyIn nematodes, a particular division of the stoma (mouthlike opening).

   The protostoma with its wall—the protorhabdion—is the major part of the stoma.

   1968, Konstantin Ivanovich Skirabin, Key to Parasitic Nematodes, volume 1

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   Conventionally, the stoma is divided into three parts: the anterior chamber or cheilostoma, the middle or protostoma, and the posterior or telostoma.

   1977, Ivan Antonovich Rubtsov, Aquatic Mermithidae of the Fauna of the USSR