FIG. 63. Diagrams of Tunicate (on the left), Amphioxus (centre), and young Lamprey (right). 



Mouth ; au, eye ; c, peribranchial chamber ; c/i, notochord ; d, alimentary canal ; g, ear ; hz, heart ; k, gills ; Ib, liver : 

 ;, nerve cord ; ;;/, brain ; ;;/, stomach ; mt, mantle ; 2, tunicate embryos. 



