ANA TOMY OF AMPHIOXUS. 



hv 



1 



mp 



Fig. 2. Diagrammatic transverse section through pharyngeal region of female 

 Amphioxus. (After LANKESTER and BOVERI, from R. Hertwig's Lehrbuch d. 

 Zoologie.) 



at. Atrial cavity, c. Dorsal coelom, separated from atrial cavity by the double- 

 layered membrane known as the ligamentum denticulatum. ch. Notochord. 

 d.n. Dorsal spinal nerve, e. Endostyle, below which is the endostylar ccelom con- 

 taining the branchial artery, f. Fin-ray of dorsal fin. g. Gonadic pouch contain- 

 ing ova. h.v. Hepatic vein lying in the narrow coelomic space which surrounds 

 /, the liver or hepatic ccecum. La. Left aorta separated from the right aorta by the 

 hyperpharyngeal (epibranchial) groove. ly. Lymph-space. mp. Metapleur. 

 my. Longitudinal muscles of myotomes ; over against the dorsal coelom these 

 muscles are arranged vertically, and form the rectus abdominis of Schneider. 

 n.t. Spinal cord. p. Pharynx, r. Excretory tubule, t.m. Transverse or subatrial 

 muscles, v.n. Ventral (motor) spinal nerve, the fibres of which have the appear- 

 ance of passing directly into the muscle-fibres. 



N.B. The connective tissue (cutis, notochordal sheath, ccelomic epithelium, 

 etc.) is indicated by the black lines 



