... the rudiments of the thymus glands. They areregion of the pharynx, ph, the tip of the forebrain, fb, the anterior edge of the heart, ht, and the curve of the tail, t. The chief point of interest ... while in the ventralwall they are more rounded. Thisdifference in the shape of the cellsaccounts for the slightly greater thickness of the floor over that of the roof of the pharynx. The gill ... region of the hindgut with the exterior. No sign of and, to some extent, in the lateral walls,there seems to be a tendency for the nucleito become collected toward the side of the wall away from the...