Myotomes 

 Gonad 



Amphioxus (Cephalochordata) 



Notochord 



Nerve cord 



Endostyle 

 Pharynx 



Adult Tunicate 

 (Urochordata) 



Balanoglossus (Hemichordata) 



Fig. 1. Types of primitive Chordata. The Hemichordata are most 



primitive; the two diagrams of the Tunicate show the degenerative 



speciaHzation of the adult; and at the top is Amphioxus, which is almost 



vertebrate in structure. 



