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Show 1906.] ANATOMY OF THE OPHIDIA. 13 The whole lengths of the two specimens which I have examined were as follows :-Specimen A, 21 inches; Specimen B, 19^ inches. The distance between umbilicus and vent was naturally greater in the larger specimen, and the umbilicus itself larger. In the above given measurements I regard as the navel not merely the actual aperture in the skin through which the yolk-plug* protrudes, but the whole area which is devoid of scaling. The yolk-plug in the interior of the body extends from the gall-bladder anteriorly to the end of the kidneys posteriorly, and lies above the fat-body. It is a dense solid plug. Meckel's diverticulum arises from it just behind the umbilicus, and enters the small intestine about an inch behind the pancreas. The umbilicus itself is so exactly median in position (text-fig. 2) that it has divided the epigastric vein, which, instead of lying to one side or the other, forms a loop surrounding it. As elsewhere this vein is single, the position of the umbilicus could, I imagine, be detected in a more fully adult snake by this splitting and rejoining of the epigastric vein. Text-fig. 2. S V.S. Region of umbilicus in newly-born Anaconda (Eunectes notceus). umb. Umbilical area; V.S. Ventral scales anterior to umbilicus, which are still divided into two; V.S'. Similar ventral scales behind the umbilicus. In the two newly-born Anacondas the area of the navel embraced nine of the ventral scales, which are split into halves, each half lying on either side of the soft median area. Anteriorly and posteriorly two scales showed a median groove, indicating, it is to * Messrs. Mole & Urich (P. Z. S. 1894, p. 505) mention the existence of " traces of the umbilical cord " in newly-born Eunectes murinus. |