104 



Comparative Morphology of Chordates 



NERVE CORD^. 



NOTOCHORD. 



^-DORSAL ARTERY 



*C ,METAPLEURAL FOLD. 



PERIBRANCHIAL CAVITY. 



GILL APERTURE'. i VENTRAL ARTERY 



Fig. 314. Diagrammatic cross section of a larval stage of Amphioxus showing 

 relations of the metapleural folds, peribranchial (atrial) cavity, and pharynx. 

 (After Gaskell. Courtesy, Neal and Rand: "Chordate Anatomy," Philadelphia, 

 The Rlakiston Company.) 



OPENI 



ING OF PERIBRANCH.CAV. 



LARVAL UROCHORDATE 



/DORSAL NERVE 



ANUS 

 POST OPENING OF 

 PERIBRANCHIAL CAVITY 



B. CEPHALOCHORDATE 



,DORS. NERVE CORD 



NTESTINE ANUS i 



C. VERTEBRATE (CYCLOSTOME) 



Fir;. 315. Diagrams of (A) larval urochordate, (B) cephalochordate (Amphi- 

 oxus), and (C) vertebrate [Petromyzon), illustrating the fundamental character- 

 istics of chordates. (After Hesse-Doflein. Courtesy, Neal and Rand: 'Chordate 

 Anatomy," Philadelphia, The Blakistou Company.) 



