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The histology of the oesophageal region of the plant parasitic nematode Xiphinema index Thorne and Allen, 1950 has been studied in cross sections of KMnO 4 -fixed nematodes. The stoma consists of cuticle, which is of different types anterior and posterior to the guide ring, and its underlying hypodermis. The latter tissue is connected through the dorsal, ventral, and lateral hypodermal chords to the interchordal hypodermis of the body wall. It is suggested that the dilator buccae muscles may act to close the stoma around the odontostyle. Stylet retractor muscles are identified. Observations on the guide ring complex support the interpretation that the guide sheath is an eversible portion of the posterior stoma cuticle. The odontostyle is embedded within the tip of the extension, which appears to be similar in composition and continuous with the posterior stoma cuticle. Cellular circumoesophageal membranes occur around the oesophagus. Those surrounding the oesophageal bulb are modified as muscle cells.
K. A. Wright (Sat,) studied this question.