SECTION THEOUGH, PHAKYNX 



191 



The cutaneous, skeletal, muscular, and nervous 

 systems are practically the same as in B. 



2. The digestive system. 



a. The pharynx has the same structure as in B, but 

 differs markedly in shape, being strongly com- 

 pressed laterally, so that its two sides are almost 



H S 



!FiQ. 42. — Amphioxus lanceolatus. Transverse section through the 

 hinder part of the pharynx of an adult female, passing through the 

 liver and ovaries. The boundary of the atrial cavity is indicated 

 by a thick black line. (a. m. m.) 



A, skeleton of dorsal fin. B, spinal cord. C, notochord. D, connective- 

 tissue sheath of notochord. E, cavity of pharynx. F, hyperbranchial 

 groove. Q-, hypobranchial groove. H, atrial cavity. L, liver. M, dorsal 

 cCBlomic canal. J^Q*, branchial ccelomic canal. 0» ccelomic' space surrounding 

 liver. OV, ovary. P, metapleural canal. R, left dorsal aorta. S, cardiac 

 aorta. T, hepatic veins. 



