Stage 35
At the Mid Body Axis Rotation Stage (CirobuD:0000058; 6-45 h), the endostyle axis is perpendicular to the axis passing through the stalk. In the branchial chamber, which is more expanded than in the previous stage, one pair of elliptical gill-slits (CirobuA:0000623), separated by a transverse bar (CirobuA:0000746), allows for filtration. The transverse bar contains the transverse sinus of the branchial sac. The peripharyngeal band (CirobuA:0000680), which is the ciliated band of the pharynx delimiting the prebranchial zone (CirobuA:0000869) from the branchial one, is visible (Ogasawara and Satoh, 1998).