Lancelet cross section
A cross section through the gill region of an Amphioxus (lancelet; phylum Chordata, subphylum Cephalochordata). Visible is the muscle tissue (striated red), gill bars and gill slits (surrounding an open cavity), notochord (touching the top-most gill bars), and nerve cord (touching the top of the notochord). Seen at approximately 40x magnification.
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