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



'^, Mouth ; au, eye ; c, peribranchial chamber ; ch, notochord ; d, alimentary canal ; g, ear ; hz, lieart ; k, gills ; Ih, 

 7n, nerve cord ; m, brain ; 7iig, stomach ; mi, mantle ; z, tunicate embryos. 



liver ; 



