40 



VERTEBRATE ZOOLOGY 



Fig. 12. — ^Transverse section of the ventral part of the pharjmx of Amphioxus. 

 c, coelom; e, endostyle; gl, endostylar glands; mba, median branchial artery; pb, 

 primary bar; sk, endostylar and branchial rods and skeletal plates; tb, tongue bar, 

 (From Herdman, after Lankester.) 



Fig. 13. — Diagrammatic transverse sections of Amphioxus to show three stages 

 (A, B, C) in the development of the atrium, ao, aorta; c, dermis; d, intestine; 

 /, fascia; fh, cavity for dorsal fin ray; m, myomere; n, neural tube; p, atrium; 

 sfh, metapleural folds; si, subintestinal vein; sfc, sheath of notochord and neural 

 tube; si, sub-atrial ridge; sp, coelom. (From Parker and Haswell, after Lankester 

 and Willey.) 



